In large saucepan or Dutch oven, cook rotini to desired doneness as directed on package, adding sugar snap peas during last 4 minutes of cooking time. Drain; return to saucepan. Cover to keep warm.
Meanwhile, in medium nonstick saucepan, heat oil over medium heat until hot. Add onion; cook and stir 5 to 7 minutes or until tender. Stir in tomatoes, basil, marjoram and pepper. Bring to a boil. Reduce heat; simmer 10 minutes.
Add tomato mixture to rotini and sugar snap peas; toss gently to coat.