Is the Roth IRA and Traditiona 401K contributions shown in box 12a and 12b on my W-2?

401k contributions are found on the W-2 in Box 12. IRAs are usually accounts you would set up yourself outside of work and would not be found on the W-2.

You could have Roth contributions with codes 

• BB -- Designated Roth contributions under a 403(b) plan
• EE -- Designated Roth contributions under a governmental 457(b) plan

A contribution to a Roth 401(k) (which is not a Roth IRA) would have code AA.