Preheat oven to 350°. Prepare cellentani pasta according to package directions.
Meanwhile, melt 2 Tbsp. butter in a Dutch oven over medium heat. Gradually whisk in flour; cook, whisking constantly, 1 minute. Gradually whisk in milk and evaporated milk until smooth; cook, whisking constantly, 8 to 10 minutes or until slightly thickened. Whisk in cheese, salt, and 1/8 tsp. ground red pepper until smooth. Remove from heat, and stir in ham, pimiento, and pasta.
Pour pasta mixture into a 13- x 9-inch baking dish coated with cooking spray. Stir together crushed cereal, 1 Tbsp. melted butter, and remaining 1/8 tsp. ground red pepper; sprinkle over pasta mixture.
Bake at 350° for 30 minutes or until golden and bubbly. Let stand 5 minutes before serving.
Note: We tested with Barilla Cellentani.
Note: Nutritional analysis is per serving, baked with topping.