Here is a tasty roast beef and cheese sandwich idea that you serve warmed with a french onion soup dip.
Melt butter in a large skillet over medium heat. Add onions and cook until tender and then add the soup and bring to a slight boil.
Stir in the roast beef and then remove from heat.
Divide the roast beef into 4 portions and layer the portions onto the rolls, topping with cheese.
Place the sandwiches under a broiler until the cheese melts.
Serve the sandwiches with the broth for dipping.