Preheat your oven to 350 degrees F.
Slice the rolls in half (lengthwise), place bottom half in a baking dish and set aside.
In a large skillet, heat olive oil over medium high heat. Add onions and green pepper and saute approximately 7 minutes (stirring frequently), or until onions and peppers are tender.
Add roast beef to mixture and cook for an additional minute to heat roast beef, stirring frequently. Season with desired amounts of salt and pepper. Remove from heat.
Spread the mayonnaise evenly over the bottom rolls and on the bottoms of the top rolls.
Spread the beef, onion and pepper mixture evenly over the bottom rolls. Evenly top with the 6 slices of provolone cheese.
Place top rolls over beef mixture and cheese. Brush tops of rolls with melted butter.
Cover with aluminum foil and bake for 10 minutes. Remove foil and bake for an additional 10 minutes. Slice rolls and serve hot.