Because all Roth IRAs that you might have are treated as one combined Roth IRA for tax purposes, a Roth IRA custodian has no way to know if a nonqualified Roth IRA distribution (code J or sometimes code T) is taxable or not. The taxable amount must be determined on your tax return.
You must click the Continue button on the page that lists the Forms 1099-R that you have entered into TurboTax, then answer the questions that follow, particularly any question asking if you had a Roth IRA prior to 2019 and any questions asking about your basis in Roth IRA contributions and conversions. TurboTax will used the answers to these questions combined with the amount of the Roth IRA distribution to determine the taxable amount of the distribution.
(MarilynG1, code B has nothing to do with Roth IRAs.)
