Cut tops off peppers; chop tops and set aside. Discard stems and seeds; set pepper cups aside. Set aside 3/4 cup spaghetti sauce; pour the remaining sauce into a 5-qt. slow cooker.
In a large bowl, combine the sausage, rice, cheese, onion, tomato, parsley, olives, garlic powder, salt, Italian seasoning, pepper flakes and reserved chopped peppers and spaghetti sauce. Spoon into peppers.
Transfer peppers to slow cooker. Cover and cook on low for 4-5 hours or until sausage is no longer pink and peppers are tender. Yield: 5 servings.