Even though there is tax withholding in box 4, you'll still need to split the Form 1099-R. All of the tax withholding goes on the split Form 1099-R that you make for the portion that was RMD. If you e-file, your filing would have in it only the details of the split Form 1099-R for the RMD and not the one for the split for the portion rolled over, so I suggest mailing your tax return and attaching Copy B of your paper Form 1099-R. That way the IRS will be unaware that you had to split the Form 1099-R to accommodate TurboTax's inability to handle this situation directly.
