Without reporting correctly, you would be underpaying taxes, and, given that you know that the filing would be incorrect, the tax return could be considered to be fraudulent. The IRS may or may not detect that underpayment by comparing the reporting on your tax return with the Form 5498 that the receiving Roth IRA custodian will generate reporting a rollover to the Roth IRA and looking at any other Forms 1099-R that you received. It's possible that the error could be detected sometime in the future after significant penalties and interest have accumulated.
