If you make your entries in the normal sequence that TurboTax guides you through, I think you will have made all of the entries needed to determine the permissible Roth IRA contribution.
A few times in past years the IRA contribution limits or MAGI threshold had not been updated for the year with the initial release of TurboTax. If you were using online TurboTax before mid-January, if you contributed the maximum or your MAGI was close to the limit you might have seen TurboTax show an excess contribution prior to the software being updated (sometime before the opening of filing season) to make the correction. Also be aware that if you are Married Filing Separately the permissible Roth IRA contribution phases out over a MAGI range of $0 to $10,000.
Regardless of the specific reason, the only way entering a Roth IRA contribution can cause TurboTax to show an increase in the federal tax due is by TurboTax calculating an excess-contribution penalty. There is no other mechanism. This question comes up numerous times on the TurboTax forum each tax year.
