Make sure that you did not inadvertently mark the IRA/SEP/SIMPLE box when entering the Form 1099-R into TurboTax.
Make sure that in the follow-up to entering the details of this Form 1099-R that you indicated that, yes, you rolled the money over to a Roth IRA account. (Be aware that TurboTax will default the answer to this question back to No if you edit this Form 1099-R and blindly step through all of the follow-up questions.)
Make sure to indicate in the follow-up that you made no after-tax contributions to the 403(b).
If checking these entries does not correct the problem, delete and reenter the Form 1099-R.
Note that having "ROLLOVER" on line 4b is correct for this transaction. The transaction is a technically a taxable rollover.
