Combine crumbs, green onions and pepper in medium bowl. Add beef; mix well. Shape into 1 1/2-inch meatballs. Place in ungreased baking pan. Bake in preheated 425 degree F oven, 10 minutes or until no longer pink inside. Drain on paper towels; set aside.
Meanwhile, heat oil in large skillet over medium-high heat. Add mushrooms and sweet pepper; cook 2 to 3 minutes or until tender. Stir in undrained tomatoes; bring to boil. Reduce heat to low. Add meatballs; cook, uncovered, 4 to 5 minutes.
Spoon meatballs and sauce onto each roll. Sprinkle each with 2 tablespoons cheese. Heat in oven 3 minutes or until cheese is melted.