Preheat oven to 350° F. Cook pasta according to package directions. Meanwhile, cook sausage in a large skillet over medium-high heat, stirring frequently, until thoroughly cooked and no longer pink. Add drained spaghetti and sauce to sausage; stir gently to blend well. Transfer mixture to a lightly greased 2-quart casserole dish; top with cheese. Bake 20 minutes or until cheese is lightly browned.