Combine spinach, mushrooms, beans, 2 teaspoons chili powder, salt and red pepper flakes in large skillet; cook and stir over medium heat 5 minutes. Combine tomato sauce, water, remaining 1 teaspoon chili power and hot pepper sauce in medium skillet.
Dip each tortilla into tomato sauce mixture. Spoon filling evenly onto center of tortillas; roll up and place seam side down in 11x8-inch microwaveable dish. Secure rolls with toothpicks, if necessary. Spread remaining tomato sauce mixture over enchiladas.
Cover with vented plastic wrap. Microwave on Medium (50%) 10 minutes or until heated through. Sprinkle with cheese. Microwave on Medium 3 minutes or until cheese is melted. Serve with desired toppings. Remove toothpicks before serving.