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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-11-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001452142</rptOwnerCik>
            <rptOwnerName>Lund John T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ROCKVILLE FINANCIAL, INC.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SOUTH WINDSOR</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06074</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP/CFO/Treasurer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-11-26</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>77</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.25</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2897</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>948.3879</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F5"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Rockville Bank ESOP Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>114.33</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F6"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Rockville Bank 401(k) Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>9.24</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2009-03-16</value>
                <footnoteId id="F7"/>
            </exerciseDate>
            <expirationDate>
                <value>2019-03-16</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6250</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6250</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.25</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2010-11-15</value>
                <footnoteId id="F8"/>
            </exerciseDate>
            <expirationDate>
                <value>2020-11-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4600</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4600</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes 200 shares held jointly with wife.</footnote>
        <footnote id="F2">Includes 1,274 restricted stock granted pursuant to the Rockville Financial, Inc. 2006 Stock Incentive Award Plan. The original grant of 1,500 shares will become vested in equal 20% increments over a five year period, the first 20% vesting on March 16, 2009 and the subsequent vesting on each annual anniversary of that date. The reported number of shares is net of 226 shares withheld by the Issuer for tax withholding purposes.</footnote>
        <footnote id="F3">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="F4">Includes 1,423 restricted shares granted pursuant to the Rockville Financial, Inc. 2006 Stock Incentive Award Plan. The original grant of 1,500 shares vest in equal 20% increments over a five year period, the first 20% vesting on November 15, 2010 and the subsequent vesting on each annual anniversary of that date. The reported number of shares is net of 77 shares withheld by the Issuer for tax withholding purposes.</footnote>
        <footnote id="F5">Shares allocated to the account of Mr. Lund under the Rockville Bank Employee Stock Ownership Plan, of which no shares are vested as of December 31, 2009.</footnote>
        <footnote id="F6">Total beneficial ownership is 3,959.7179 at 11/26/2010.</footnote>
        <footnote id="F7">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 March 16, 2009 and the subsequent vesting on each annual anniversary of that date.</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 November 15, 2010 and the subsequent vesting on each annual anniversary of that date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Marliese L. Shaw by POA</signatureName>
        <signatureDate>2010-11-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
