After you answer Yes to the question that asks if the distribution came from an inherited account, TurboTax normally asks you to specify the taxable amount since it can depend on when the decedent first opened a Roth IRA and perhaps the amount of Roth IRA contributions and conversions made by the decedent. TurboTax then places this amount into box 2a to record the entry. If TurboTax does not ask how much is taxable, enter the taxable amount directly into box 2a of TurboTax's 1099-R form.
