Cook sausage, onions, peppers and oregano in a large skillet over medium-high heat, stirring frequently, until meat is thoroughly cooked and no longer pink. Stir in garlic and spaghetti sauce, reduce heat to low; simmer five minutes. Preheat oven to 375° F. Hollow out each roll with a knife, leaving a 1/2-inch shell. Fill rolls with sausage mixture. Cover with mozzarella slices. Bake directly on oven rack for 20 minutes. Serve whole, or for appetizers cut into 1 1/2-inch slices; sprinkle with crushed red pepper, if desired.