These Low Calorie Roast Beef Sandwiches are just 253 calories, and that includes the "Copycat" sauce!I was able to make this recipe extra low calorie with the help of my low calorie burger buns. But you can use store-bought if you prefer. Special Tip: To cut the calories and carbs in store-bought burger buns simply cut the buns in half and hollow out the centers. This will save you about 1/3 of the calories and carbs!