Retirement 401K plans are before tax or after tax dollars.
A contribution to a Traditional 401K reduces the amount of wages you are taxed on. However when money is then taken out of Traditional IRA it is taxed.
A contribution to a Roth 401K does not reduce the amount of wages you are taxed on. However when money is then taken out of Roth IRA it is not taxed.
TurboTax is asking that question as if it is rolled from a Traditional 401K (which I assume you had) to a Roth 401K you will pay the tax on it now.
If you are unsure, check with the HR office with your company.
You probably rolled over from a Traditional 401K to a Traditional 401K, which would have no tax impact, however you need to be sure.
