Slice the top off each roll to make a lid, then hollow out the rolls. (The insides can be used for bread crumbs later, if desired.) Place on a baking sheet, and toast the rolls for 5 minutes at 350 degrees.
In a lightly oiled skillet, saute the onion until starting to soften and brown a bit. Add meatloaf and crumble. Stir in enough pizza sauce to coat, then fill the rolls with the meat mixture.
Top with a little more sauce, a tablespoon or two of cheese, and a few pepperonis, if desired. Bake 5 more minutes or until cheese is melted and everything is heated through. Put lid on and enjoy!
