Preheat oven to 375'F. Cook macaroni as directed on package; drain and set aside. Melt margarine over low heat. Stir in flour; cook 1 minute, stirring constantly until mixture is smooth and bubbly. Stir in milk; heat to a boil, stirring constantly. Reduce heat and simmer until thickened, about 1 minute. Add cheese and Ro*Tel. Stir until cheese is melted, remove from heat. Stir macaroni into cheese sauce. Transfer to an ungreased 9x12" baking dish. Bake uncovered 30 minutes or until heated through.