Section 401(a)(31) of the tax code requires that they allow a direct rollover on any eligible rollover distribution, so if they allow in-service distributions, they are also required to allow a direct rollover of the otherwise taxable portion of such a distribution. Since they are only required to allow a direct rollover of the taxable portion of a distribution, if you are doing a split rollover of pre-tax and after-tax amounts, a plan will often do the direct rollover to a traditional IRA of the pre-tax amount, avoiding mandatory 20% tax withholding, and will pay the after-tax amount to you (with no tax withholding because this portion is nontaxable) which you can then roll over indirectly within 60 days to a Roth IRA.
