Amounts reported in box 12 of your W-2 are to be entered only in box 12 of TurboTax's W-2 form, nowhere else in TurboTax. You Roth 401(k) is not a Roth IRA, so no entry should be made under Deductions & Credits for the Roth 401(k) contribution. Go back and remove the entry that you made there.
