Your contributions reported with code AA in box 12 of your W-2 are contributions to a Roth 401(k), not a Roth IRA.  Enter this only on TurboTax's W-2 form, nowhere else in TurboTax.

Roth contributions are not deductible or excludible from income.  If you qualify for the Retirement Savings Contributions Credit, TurboTax will automatically include the amount entered with code AA in box 12 of TurboTax's W-2 form when figuring this credit.