The entire interest of the Roth must be distributed by the end of 10 years in the year of the owner's death. You can also read more about it on Pub 590-B under the Roth IRA section.
See below: Taken from Pub 590-B
Distributions After Owner's Death
If a Roth IRA owner dies, the minimum distribution rules that apply to traditional IRAs apply to Roth IRAs as though the Roth IRA owner died before their required beginning date. See When Can You Withdraw or Use Assets? in chapter 1.
Distributions to beneficiaries.
Generally, the entire interest in the Roth IRA must be distributed by the end of the 5th or 10th calendar year, as applicable, after the year of the owner's death unless the interest is payable to an eligible designated beneficiary over the life or life expectancy of the eligible designated beneficiary. See When Must You Withdraw Assets? (Required Minimum Distributions) in chapter 1.
If paid as an annuity, the entire interest must be payable over a period not greater than the designated beneficiary's life expectancy and distributions must begin before the end of the calendar year following the year of death. Distributions from another Roth IRA can't be substituted for these distributions unless the other Roth IRA was inherited from the same decedent.
