Preheat oven to 350°. Prepare pasta according to package directions. In large skillet, cook bacon till done. Remove and drain all but about 2 tbsp. bacon grease. Add onions and mushrooms—cook till onions soften. Add Rotel, chicken and bacon. Mix this with the cooked pasta; add jar of alfredo sauce and the dry ranch mix. Pour into greased 13×9 baking dish and bake for 20 min. Remove from oven and top w/cheese. Bake 10 min. more. Remove from oven and stir cheese into casserole; serve.