We love roast beef, and we love to use the leftovers in various ways.
Stew/Soup. Rolled in tortillas with black beans, cheese, and salsa.
Last night, I used the last of our leftover roast for what I call "Roast Beef Hash." It's easy, and really good comfort food, in my opinion. I started cooking an onion in "Extra Virgin Olive Oil"-or EVOO as Rachael Ray calls it. Enough to cover my skillet bottom and keep things from sticking, but not enough for deep frying. (My amounts are vague here, as it all depends on how much onion, potato, and beef you want to cook.) After your onions are cooked to perfection, soft and sweet, you can remove them to add later or, as I like to do, leave them as they are to get crispier.
After the onions have spent some time getting happy in the oil, I add chopped potatoes. Here I am using yellow potatoes with the skins on. They are thin and tasty. I love not having to remove potato skins. Cook them on medium heat to crisp and steam cook in the oil.
Then, when the potatoes are nearly done, add chopped cooked roast beef. You are just frying them together for a while, to get a little crispy. When I do this, the beef still tastes tender. I imagine if you add it too early or let it sit too long, it may get dry.
The finished hash. My kids like this with a little ketchup. Don't forget the pepper and salt! Serve with veggies.