For a code 2B Form 1099-R, TurboTax asks a question that serves no purpose other than the trip you up. Edit this 1099-R form in TurboTax and in the follow-up indicate that this distribution was NOT from a Roth IRA. The code B explicitly indicates that the distribution was from a Designated Roth Account in 401(k), 403(b) or 457(b) plan, not from a Roth IRA.
