Find the places where the thigh bones have been removed from the chicken, and stuff the spaces with sausage. Place on a 10x13-inch ungreased baking pan. Place bell pepper and onion around the chicken. Pour tomatoes and their juices over the chicken, and season with Italian seasoning and crushed red pepper flakes.
Bake in preheated oven until chicken is thoroughly cooked, about 45 minutes.
