In 4-quart saucepan, heat oil over medium heat. Add onion; cook and stir until softened. Add flour; cook and stir until moistened. Gradually add milk, cooking and stirring about 2 minutes or until smooth and bubbly.
Stir in pasta sauce, tomatoes and broth. Cover; cook over medium heat about 15 minutes, stirring frequently, just until mixture boils. Top each serving with 3 tablespoons cheese.