[header] How to use leftover roast [title] Make beef broth. [step] You can make a rich beef broth to have on its own or use the broth as a base for soups and stews. To make the broth, just saute large pieces of the leftover roast beef along with one diced onion. 
Once the onion is soft, add enough water to cover the meat. Bring this to a light boil and keep cooking until the water darkens.