In 4-quart Dutch oven or stockpot, cook pasta as directed on package.
Meanwhile, in 3-quart saucepan, melt butter over medium heat. With whisk, beat in flour until well combined and mixture bubbles slightly. Beat in milk, cooking and stirring 7 to 8 minutes or until mixture is slightly thickened but not boiling.
Add cheese, salt and pepper; stir until cheese melts. Stir roasted red peppers and artichoke hearts into cheese sauce. Remove from heat.
Drain pasta; return to Dutch oven. Pour sauce over pasta. Add chicken; stir well to combine. Sauce will thicken upon standing.