<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>0010 - Disclosure - 4. Property and Equipment</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>From2011-07-01to2012-06-30</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0001020477</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2011-07-01T00:00:00</PeriodStartDate><PeriodEndDate>2012-06-30T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="12 Months Ended" /><Label Key="Calendar" Id="1" Label="Jun. 30, 2012" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>ROBK_NotesToFinancialStatementsAbstract</ElementName><ElementPrefix>ROBK_</ElementPrefix><IsBaseElement>false</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Notes to Financial Statements</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="From2011-07-01to2012-06-30" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;As of June 30, 2012 and 2011, property
and equipment consisted of the following&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in"&gt;&amp;#160;&lt;/p&gt;

&lt;table cellspacing="0" cellpadding="0" style="font: 8pt Calibri, Helvetica, Sans-Serif; width: 100%"&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: center; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="border-bottom: black 1.5pt solid; text-align: center; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;&lt;b&gt;2012&lt;/b&gt;&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="text-align: center; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: center; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="border-bottom: black 1.5pt solid; text-align: center; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;&lt;b&gt;2011&lt;/b&gt;&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: #CCEEFF"&gt;
    &lt;td style="width: 78%; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Gaming vessel&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 8%; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;-&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="width: 1%; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 8%; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;4,854,908&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="width: 1%; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: white"&gt;
    &lt;td style="line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Truck&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;-&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;39,761&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: #CCEEFF"&gt;
    &lt;td style="line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Furniture and fixtures&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;8,490&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;8,490&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: white"&gt;
    &lt;td style="line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Office equipment&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;23,289&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;23,290&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: #CCEEFF"&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;31,779&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;4,926,449&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: white"&gt;
    &lt;td style="line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;&amp;#160;&amp;#160;&amp;#160;Less accumulated depreciation&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;(29,532&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;)&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;(263,708 &lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;)&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: #CCEEFF"&gt;
    &lt;td style="line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;&amp;#160;&amp;#160;&amp;#160;Sale of Gaming Vessel&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;-&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1.5pt solid; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;(4,651,637 &lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;)&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: white"&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;2,247&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;11,104&lt;/font&gt;&lt;/td&gt;
    &lt;td nowrap="nowrap" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;
&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;On June 10, 2010, the Company purchased The Big Easy, a gaming
vessel for an aggregate purchase price of $4,264,500, payable: (a) by issuance of a secured note payable to the seller of $2,975,000
(the Secured Note), (b) issuance of an unsecured note payable to the seller of $600,000 (Unsecured Note), fees of $414,500 and
cash of $275,000. As of September 17, 2010, both notes were in default and the interest rate was increased to 20%, per annum. As
of June 30, 2011, the Big Easy was sold at public auction at a loss of $4,191,891 (Note 9).&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;On December 1, 2011, the Company transferred ownership of
the Company truck to an officer without consideration.&amp;#160;&amp;#160;The vehicle had a net book value of $0 at the date of transfer.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;Casino construction in progress totals $538,853 and represents
expenses related to the architectural design of the casino.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;For the years ended June 30, 2012 and 2011, depreciation expense
was $8,857 and $214,066, respectively.&lt;/p&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>The entire disclosure for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, accounting policies and methodology, roll forwards, depreciation, depletion and amortization expense, including composite depreciation, accumulated depreciation, depletion and amortization expense, useful lives and method used, income statement disclosures, assets held for sale and public utility disclosures.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

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