<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-12-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001311131</issuerCik>
        <issuerName>Rockville Financial Inc.</issuerName>
        <issuerTradingSymbol>RCKB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001313367</rptOwnerCik>
            <rptOwnerName>Rosner Laurie A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ROCKVILLE FINANCIAL INC</rptOwnerStreet1>
            <rptOwnerStreet2>1645 ELLINGTON ROAD</rptOwnerStreet2>
            <rptOwnerCity>SOUTH WINDSOR</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06074</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>SVP/Rockville Bank</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10367.608</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Rockville Bank 401(k) Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5484</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Held by husband</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-12-26</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>377</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.01</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>15533</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3673.8809</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F6"/>
                    <footnoteId id="F7"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Rockville Bank ESOP Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>17.77</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2008-12-13</value>
            </exerciseDate>
            <expirationDate>
                <value>2016-12-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>14.35</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2007-08-14</value>
                <footnoteId id="F8"/>
            </exerciseDate>
            <expirationDate>
                <value>2017-08-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.98</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2008-02-20</value>
                <footnoteId id="F9"/>
            </exerciseDate>
            <expirationDate>
                <value>2018-02-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes non-reportable shares acquired in the Rockville Bank 401(k) Plan during the third quarter 2008 for Ms. Rosner, not previously reported of 29.1798 shares purchased on 7/7/2008, 28.0233 shares purchased on 7/17/2008, 24.4083 shares purchased on 8/5/2008, 25.6796 shares purchased on 8/24/2008, 27.2215 shares purchased on 9/7/2008, 26.7315 shares purchased on 9/28/2008,  and 35.0018 shares purchased on 9/30/2008.</footnote>
        <footnote id="F2">Includes 5,120 shares held jointly with husband.</footnote>
        <footnote id="F3">Includes 4,261 restricted shares granted pursuant to the Rockville Financial, Inc. 2006 Stock Incentive Award Plan. Of the original 6,000 shares granted 20% vested on December 22, 2006, December 13, 2007, and December 13, 2008, and 20% will vest on each December 13 of years 2009 and 2010. The reported number of shares is net of 1,311 shares withheld by the Issuer for tax withholding purposes.</footnote>
        <footnote id="F4">Includes 3,699 restricted stock granted pursuant to the Rockville Financial, Inc. 2006 Stock Incentive Award Plan. The original grant of 4,000 shares will become exercisable in equal 20% increments over a five year period, the first 20% becoming exercisable on February 20, 2008 and the subsequent vesting on each annual anniversary of that date. The reported number is net of 301 shares withheld by the Issuer for tax withholding purposes.</footnote>
        <footnote id="F5">Transaction representing shares withheld by the Issuer for tax withholding purposes with respect to the vesting of and removal of restrictions on Restricted Stock previously issued to the Reporting Person by the Issuer under its 2006 Stock Incentive Award Plan.</footnote>
        <footnote id="F6">After the transaction dated December 26, 2008 total beneficial ownership is 35,058.4889 shares.</footnote>
        <footnote id="F7">Shares allocated to the account of Ms. Rosner under the Rockville Bank Employee Stock Ownership Plan, of which 3,673.8809 shares are vested.</footnote>
        <footnote id="F8">Stock options granted pursuant to the Rockville Financial, Inc. 2006 Stock Incentive Award Plan and will become exercisable in equal 20% increments over a five year period, the first 20% becoming exercisable on August 14, 2007 and the subsequent vesting on each annual anniversary of that date.</footnote>
        <footnote id="F9">Stock options granted pursuant to the Rockville Financial, Inc. 2006 Stock Incentive Award Plan and will become exercisable in equal 20% increments over a five year period, the first 20% becoming exercisable on February 20, 2008 and the subsequent vesting on each annual anniversary of that date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Laurie A. Rosner</signatureName>
        <signatureDate>2008-12-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
