The IRS has clarified that if an IRA owner had already reached his or her required beginning date for withdrawals, the beneficiary must begin annual RMDs in the first calendar year after the owner’s death. The remaining account balance must still be distributed by the 10th calendar year after the account owner’s death. In other words, an RMD is required in years 1-9 when the decedent had already begun taking RMDs.
A non-spouse beneficiary that is a designated beneficiary (but not an "eligible beneficiary") must follow the 10-year rule. This rule requires that RMDs be empty the entire account by the end of the 10th year following the year of the account owner's death.
Inherited Roth IRAs
This same IRS document indicates that generally, inherited Roth IRA accounts are subject to the same RMD requirements as inherited traditional IRA accounts. Withdrawals of contributions from an inherited Roth are tax free. Most withdrawals of earnings from an inherited Roth IRA account are also tax-free. However, withdrawals of earnings may be subject to income tax if the Roth account is less than 5-years old at the time of the withdrawal.
Distributions from another Roth IRA cannot be substituted for these distributions unless the other Roth IRA was inherited from the same decedent.