An idea for a leftover pot roast is one that my grandmother, mother, and now I use: Cut up or shred some of the beef and save it for the next day along with some potatoes and carrots (as little or as much as you like). Grandma calls it "hash".
Cut 2 slices of bread into small squares, melt a little margarine in a large skillet. Lightly brown the bread, add the beef, cut up potatoes, and carrots, and anything else you'd like to throw in. While this is heating through, beat 2 eggs in a bowl then add it to the skillet. Cook 'til the eggs are done. It may not sound great, but it sure is delicious. Stretch the recipe a bit with some throw-in ideas: green beans, corn, peppers, onions. Enjoy!