Man, that seems like a lot of work and time that I just don't seem to have right now..
My original plan to get the pi3 with just Retropie & controllers failed as my wife wanted to make other purchases on Amazon and by the time she went to order there were no pi3 with just retropie and the controllers available...
So we ended up going with
pi3 with Retropie, Kodi and controllers
Will have to re-purpose the Roku3 now for another room but, in theory, all I need to do is get the ROM's we want added to a USB drive and Christmas morning get to playing