Grandma always used the leftover roast beef, gravy and whatever vegetables were on hand to make shepherd's pie. liberally grease your dish or baking pan. Dice the meat and add whatever's leftover, diced. If you're out of gravy, Packaged gravy mix isn't bad if you doctor it up a bit, add some cooked taters, carrots, onion, a dash or two of garlic powder, a dash of what's this here sauce, frozen veggie mix can be pre-cooked in the microwave then added to the pie if you're out of veggies, or a can of the mixed ones, drained, can do in a pinch. Mix it all up, pour it in the dish, then top it with biscuits and bake it til the biscuits are done and the pie is bubbly. Make your own drop biscuits, rolled biscuits or use 'whomp rolls'...just make sure the underside of the biscuits are done before you pull it out of the oven. Lift one up with a fork, test it to make sure it's cooked.
(I recently had one that the underside of the biscuit was still raw...UG!)
"Chinese" style noodles with the leftover roast, diced, stir fry any chinese style veggies you like, pea pods, mushrooms, etc, and make a sauce with any leftover gravy and soy sauce, garlic, white pepper, five spice powder and maggi's, if you have them. Saute' the veggies a bit, add the sauce fixin's and then warm it all up and stir fry the noodles in it. If you like the 'hot and sour' type, add a dash of vinegar and a shot of some hot red oriental sauce or tabasco, and more white pepper.
We also make a slurpy-noodle soup with basically the same ingredients, just more water or broth to float the noodles.
Top either with diagonally-diced green onion.
mmm.. makin' me wish we had some leftovers in the fridge.