1In a large frying pan,heat the oil over moderate heat. Add the sausage and cook stirring for 3 minutes. Stir in the onion,celery,green pepper and garlic. Cover the pan and cook over moderately low heat, stirring occasionally,until the vegetables are soft,about 10 minutes. Add the tomatoes,salt and black pepper. Cover and simmer for 15 minutes longer.
2In a large pot of boiling,salted water,cook the rigatoni until just done, about 14 minutes. Drain and toss the pasta with the sauce.