Prepare pasta according to package directions; drain.
Meanwhile, in large skillet, heat oil over medium-high heat. Add sausage, onions and peppers; sauté until onions are softened (about 5 minutes).
Add in shrimp and Cajun seasoning. Sauté until shrimp is opaque. Add in Alfredo sauce and simmer until heated through.
Toss with pasta, tomatoes and Parmesan cheese.