I guess the best way to do it would be to quit your job or retire or whatever, on Jan.01.
That way your "income" would be zero for the year.
What tax bracket does "zero income" fall into?
My understanding is that the rollover into the Roth, the rollover amount is treated like "income" and the amount of taxes you pay is based on what tax braket you fall into.
But I don't know because I haven't been able to find any REAL clear info on the subject.
I'll know, I guess, later this summer when I do the transfer.
Anyone reading these post should seek expert advice before taking any actions with their 401k, IRA or Roth.