Preheat oven to 375°. In a large saucepan, place a steamer basket over 1 in. of water. Place sweet potato, onion and red pepper in basket. Bring water to a boil. Reduce heat to maintain a simmer; steam, covered, until tender, 15-20 minutes., Transfer vegetables to a large bowl. Mash vegetables, gradually adding cilantro, spices and pepper to reach desired consistency. Stir in black beans., Spread 1/3 cup enchilada sauce into a greased 13x9-in. baking dish. Place 1/3 cup vegetable mixture in center of each tortilla; sprinkle with 4 teaspoons cheese. Roll up and place in prepared dish, seam side down. Top with remaining enchilada sauce; sprinkle with remaining cheese., Bake, uncovered, until casserole is heated through and cheese is melted, 20-25 minutes. If desired, serve with optional toppings.