Starting with the bottom half of the sandwich, in this order, add roast beef (as much or as little as you like), BBQ sauce, cheese, french fried onions, banana peppers. Wrap sandwich in foil and bake @ 350 degrees for 15-20 minutes or until cheese is melted and roast beef is warm. Take foil off of sandwich, flip upside down and take top half of bun off, add horse radish sauce, replace bun. Flip entire sandwich right side up and enjoy!