Preheat oven to 350°F. Coat four 12- to 14-ounce individual casseroles with cooking spray; set aside. Coat a large nonstick skillet with cooking spray; heat skillet over medium heat. Add sausage, mushrooms, onion, and garlic. Cook for 8 to 10 minutes or until bulk sausage (if using) is no longer pink and vegetables are tender, using a wooden spoon to break up bulk sausage as it cooks. Drain off fat.
Stir barley, pasta sauce, 1 cup of the cheese, the roasted pepper, olives, and 1 tablespoon of the basil into sausage mixture. Divide mixture among the prepared casseroles. Cover with foil.
Bake for 30 minutes. Sprinkle with the remaining ½ cup cheese. Bake, uncovered, about 10 minutes more or until heated through and cheese is melted. Top casseroles with tomatoes and the remaining 1 tablespoon basil.
