Easy Roast Beef and Gravy Sandwiches (crock pot)

If you want something simple, buy some precooked roast beef from your favorite local deli and use that? Deli roast beef is not all that expensive and, depending on the deli, very tasty. All you need to do is dump a can or two of au jus sauce gravy and the roast beef (maybe about 1/2 pound per person) in the crock pot about an hour before serving and set it on high. It isn't going to get any easier than that and the results will be tasty.