While your modified adjusted gross income (MAGI) will impact the amount that you can contribute to your Roth IRA, it will not impact the amount that you can transfer from a Roth 401k including a Roth solo 401k to a Roth IRA. Therefore, you could open a Roth IRA and only transfer the Roth solo 401k funds to it without having to make annual contributions to it even if your MAGI is too high.
However, in order to transfer Roth 401k including Roth solo 401k funds to a Roth IRA you must need a plan triggering event such as being age 59 1/2 or older or no longer self-employed.
