What the original poster was talking about is technically an In-plan Roth Rollover (IRR). Some refer to this as a conversion due to the similarity with a Roth conversion from a traditional IRA, but in the tax code the term "conversion" only refers to the movement of funds from a traditional IRA to a Roth IRA.
The Roth account in your 401(k) is referred to in the tax code as a "designated Roth account" in the plan.
When entering the code-G Form 1099-R into TurboTax, answer Yes to the first question asking of the funds were moved to a Roth 401(k) or similar Roth account account (not a Roth IRA). The taxable amount should be present in box 2a of the form while the nontaxable amount should be present in box 5.
