In a large saucepan, heat oil over medium heat. Add leek and garlic; cook for 5 minutes. Add broth, the water, and, if desired, crushed red pepper. Bring to boiling.
Add broccoli rabe, undrained tomatoes, ravioli, and rosemary. Return to boiling; reduce heat. Cover and simmer for 7 to 8 minutes or until broccoli rabe and ravioli are tender. If desired, sprinkle each serving with cheese. Makes 4 servings.