TurboTax does not specifically ask for a Form 5498. TurboTax only indicates that Form 5498 is a place that you can find the amounts contributed to a particular IRA for the year.
The Roth IRA custodian most certainly must issue you a 2018 Form 5948 from the Roth IRA showing the conversion contribution (assuming that this occurred in 2018). However, it's not required to be issued until sometime in May, so to be able to file by April 15 you'll likely need to use your own records to determine the amounts to enter in response to the follow-up questions to entering the Form 1099-R.
