For a code G Form 1099-R reporting a split distribution, the first Form 1099-R for the after-tax portion (the original Form 1099-R's box 5 amount) rolled over to the Roth IRA would have the box 5 amount in boxes 1 and 5 and a zero in box 2a. In the follow-up, answer that the entire amount was deposited into a Roth IRA. For the other Form 1099-R for the pre-tax amount rolled over to the traditional IRA, the Form 1099-R will have the remainder of the box 1 amount (original box 1 minus box 5) in box 1 and zeros in boxes 2a and 5. In the follow-up, indicate than none of this money went to any kind of Roth account. The boxes on the split Forms 1099-R should total to the amounts on the original Form 1099-R. The rest of the entries on TurboTax's 1099-R forms should match the original.
Since a code G Form 1099-R should have no tax withholding shown in box 4, the details of the entered 1099-R forms are not included in your e-filing. Only the result is (seamlessly) shown, on Form 1040 line 16 or Form 1040A line 12. The IRS will be unaware that you entered this by splitting the original Form 1099-R.
If the Form 1099-R instead has code other than G, the answer will be different.
