Score the sausages every 1/2 inch. cook sausages in a large skillet for 15 minutes or until browned and cooked through, drain on paper towels.Pour off drippings, reserving 3 tabespoons drippings, place reserved drippings back into skillet.
Add onions to skillet, and saute until tender. Stir in green peppers,salt, sugar, and Italian seasonings. Cover and cook 5 minutes. stir in tomatoes , if desired.Place sausage on top ,cook covered 5 minutes more until mixture bubbles.
Meanwhile, cut out the center or rolls to make boat-shaped shells. Spred 1/2 teaspoon butter on the inside of each roll. Place rolls on a baking sheet and bake at 350 degrees for 10 minutes. Divied the mozzarella cheese evenly over the hoagie rolls. Place one sausage in each roll, top with onion mixture.