Prepare rigatoni according to directions on box. Remove sausage meat from casing, set aside. In hot skillet saute onions. Add pepper and crumbled sausage meat. Stir and cook over medium high heat for 5 minutes. Add garlic and red pepper flakes. Add chicken stock and bring to a simmer. Add florets and cover to steam. Once broccoli is tender add rigatoni to pan. Stir to coat. Serve.