Cook rotini to desired doneness as directed on package. Drain.
Meanwhile, heat oven to 350°F. Spray 2-quart casserole with nonstick cooking spray. Spray medium saucepan with nonstick cooking spray. Heat saucepan over medium-high heat until hot. Add onion and chile; cook and stir 2 to 4 minutes or until crisp-tender. Remove from heat.
Add milk and sauce mix; stir until well blended with wire whisk. Bring to a boil, stirring constantly. Reduce heat to low; simmer 1 minute. Stir in both cheeses until melted.
Add cooked rotini; mix well. Spoon into sprayed casserole. In small bowl, combine chips and margarine; mix well. Sprinkle over rotini mixture.
Bake at 350°F. for 25 to 30 minutes or until bubbly and golden brown.