For meatballs:
In a medium bowl combine ground beef, bread crumbs, milk, parsley, egg, salt, pepper and mustard; mix thoroughly. Shape into one inch balls.
In a large skillet heat the oil over medium high heat. Fry meatballs in batches, turning until golden brown. Drain on paper towel.
In a seperate skillet sauté onions until golden. Add flour and garlic; cook stirring for 30 seconds. Gradually stir in beef broth; bring to a boil. Add tomatoes, tomato paste, thyme, bay leaf and meatballs; cover and reduce heat to low. Simmer for 30 minutes.
Meanwhile slice carrots diagonally, slice zucchini and green pepper. Add carrots to stew; cover and simmer for 10 minutes. Add zucchini and green pepper; cover and simmer for an additional 5 minutes longer or until vegetables are tender crisp.
In a pot of boiling water cook rotini noodles until al dente (tender but firm). Drain; stir into stew.