If the trust is the beneficiary of the Roth IRA, the 5-year rule would apply only if the trust was not qualified for look-through. If the trust meets the requirements for being qualified for look-through (one of the requirements being that the IRA custodian is provided with a copy of the trust document by the end of the year following the year of death), RMDs are based the beneficiary of the trust (or if there are multiple beneficiaries, RMDs are based on the beneficiary with the shortest life expectancy; separate accounts treatment is not permitted with a trust being the beneficiary).
But I'll ask again, what purpose would you have for making the trust the primary beneficiary in the first place? If you have no specific purpose for making a trust the beneficiary, it makes no sense to do so instead of making the beneficiary of the trust the beneficiary of the IRA directly. Making the trust the beneficiary for no particular purpose only adds complexity and potential restrictions compared to naming the individual beneficiary directly. If the trust beneficiary is allowed unrestricted access to the fund in the inherited Roth IRA, it would seem that the trust would be serving no purpose with respect to the Roth IRA.
Also, distributions from an inherited Roth IRA are not unconditionally nontaxable. Distributions of earnings in the inherited Roth IRA are taxable if distributed before the end of the 5-year period beginning on January 1 of the year for which the decedent first made a Roth IRA contribution. Earnings come out last. Unless the beneficiary actually needs the funds to spend, it generally makes sense to leave the money in the inherited Roth IRA as long as possible to gain the most tax free earnings. Unless the beneficiary was extremely old, it's unlikely that earnings would be required to be distributed before the Roth IRA completed the 5-year qualification period.
