When the pot roast is almost done prepare a non-stick skillet with 1 tablespoon olive over medium low heat. Add onion slices and toss to coat with oil. Cook for 20 to 25 minutes, until onions are soft and carmelized.
Slice rolls in half and add pile of shredded pot roast, carmelized onions, and swiss cheese.
It is always a option to add condiments like mayonnaise, horseradish, and mustard to your sandwich.