I thought traditional IRA and Roth IRA contributions were on my W2 - do I need to enter them separately in this deductions and credits section?

I think perhaps you are confusing a 401(k) with an IRA.  Also, Roth plans are post-tax, so there is no deduction for them. 

If you contributed to a Roth 401(k) or a traditional 401(k) through your workplace, you should not enter that information in the IRA section.  The contributions would have already been properly accounted for in your W-2.

Here is some more information you may find helpful: IRA vs 401(k): Which Should I Invest in First?