First you said Roth 401(k), now you say Roth IRA. Either way Roth accounts are always after tax so when you change from a pre-tax 401(k) to an after-tax Roth, you must pay the tax on it. Unless the 401(k contained after-tax contributions which would be shown in box 5 on your 1099-R for the 401(k) distribution. Assuming you 2099-R had a code G in box7 then the interview will ask if you had after-tax contributions where you enter the box 5 amount if any.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
