Baked Ravioli and Cheese

1 (50-count) package frozen cheese ravioli
2 tablespoons butter or margarine
2 tablespoons flour
2 cups milk
1 1/2 cups cubed American cheese
3/4 cup crushed potato chips (optional)

Cook ravioli according to package directions; drain.

Meanwhile, for sauce, melt margarine in a large saucepan. Stir in flour. Add milk; cook and stir until slightly thickened and bubbly.

Add cheese; heat and stir until cheese is melted. Salt and pepper to taste. Add cooked ravioli; stir gently. Spoon into an 8-inch square baking dish. Sprinkle crushed potato chips over. Bake at 350 degrees F for 15 to 20 minutes or until edges bubble and top is golden brown.