Cook pasta according to package directions, omitting salt and fat. Drain well.
Melt butter in a small saucepan over medium heat. Stir in flour, salt, and red pepper; gradually add milk, stirring with a whisk until blended. Cook 5 minutes or until thick, stirring constantly. Add cheese; stir until cheese melts. Add pasta and Chicken-Vegetable Toss; cook 3 minutes or until thoroughly heated. Serve immediately.