Preheat oven to 425 degrees Fahrenheit. Arrange sweet potato, cauliflower, peppers, and onions on a large baking pan. Toss with olive oil, sprinkle with cumin, oregano, salt, and cayenne, then toss again. Roast for 20-25 minutes, flipping once or twice during cooking, until vegetables are tender.
Reduce oven temperature to 350 degrees F.
Transfer the warm roasted vegetables to a large bowl, then add black beans, ½ cup cheese, ½ cup sour cream, and ½ cup enchilada sauce. Stir to combine.
Spread ½ cup of enchilada sauce on the bottom of a 9x13 casserole pan. Spoon ½ cup of filling into each tortilla, topping with 2-3 tablespoons of cheese before carefully rolling them tightly. Place each rolled tortilla, seam-side down, in the pan, nesting them side by side. Cover with 1 cup sauce and remaining cheese.
Cover with foil and bake for 15-20 minutes. Remove foil and bake for an additional 5-8 minutes until the cheese is bubbly. Serve with sour cream, avocado, cilantro, and lime wedges.