In TurboTax you must split the single Form 1099-R for the distribution from the 401(k) into two, one for the portion rolled over to the Roth IRA and the other for the portion rolled over to the traditional IRA such that the dollar amounts on the two split forms sum to the same amount as is in the corresponding box on the original. You'll put the box 5 amount on the Form 1099-R that corresponds to the rollover to the Roth IRA.
