No. Roth IRAs can only be transferred to another Roth IRA regardless if it was funded and/or contains funds that were transferred in from a former employer designated Roth 401k.
Bottom line once the former employer Roth 401k was transferred to the Roth IRA, the Roth 401k loses its Roth status and is now considered a Roth IRA. As a result, because the IRS rules do not allow for the transfer of a Roth IRA to a Roth 401k including a solo 401k the Roth IRA can’t be transferred to the Roth solo 401k. This same rule applies to non-deductible IRA contributions (the basis)–that is, the IRS rules don’t allow for the transfer of the non-deductible IRA basis to a Roth 401k including a Roth solo 401k
Any amounts distributed from a Roth IRA may be rolled over or transferred only to another Roth IRA and may not be rolled over to a designated Roth account. This rule applies even if the Roth IRA contains only amounts attributable to a rollover distribution from a designated Roth account. However, the gains in the non-deductible IRA may be transferred to a pre tax solo 401k, with the basis converted to a Roth IRA.
