Well, that sounds better than Hungarian Leftover Roast Casserole.
The Deputy Headmistress was looking for recipes for leftover roast beef, and this is what I usually do with ours. It's one of those no-real-amounts recipes, which makes it hard to write out. But these are the basics:
You need 1 good chunk of leftover roast, chopped into small (fork-sized) pieces; 1 small onion, sliced; at least 1 clove garlic, chopped; sliced carrots; salt, pepper, 1 tsp. paprika, and a can of tomato soup. Bake this in a covered casserole for an hour, or put it in the crock pot for the afternoon. When it's heated through and the carrots are cooked, you can add a can of green beans, if you want to stretch it a bit, and a large spoonful of sour cream; you might put it back into the oven for a few minutes to warm up the beans. We usually eat this with noodles or perogies (the little potato-stuffed ones from the supermarket).
Mushrooms might be a good addition, too. If the sauce is too runny, you can thicken it with flour or cornstarch (mix the cornstarch with the sour cream before adding).