Preheat the oven to 400 degrees.
Cook the brown rice according to package instructions. Get the rice cooking first because it takes the longest to cook and you can work on the other steps while the rice is cooking. When it's done, take the rice off the heat and set it aside.
While the rice is cooking, chop the sweet potatoes into small 1-inch cubes. Arrange the sweet potatoes on a parchment-lined tray and drizzle 1-2 tbsp of vegetable broth over the potatoes (this will help the seasonings stick without using any oil). Sprinkle 1 tsp chili powder, 2 tsp smoked paprika, 1 tsp cumin, 1 tsp garlic powder, 1 tsp onion powder, ¼ tsp salt, and ¼ tsp black pepper over the sweet potatoes. Toss to coat each piece in the seasonings and then bake the potatoes for 20 minutes.
While the sweet potatoes are roasting, saute the diced onion in 3-4 tbsp of low-sodium vegetable broth in a large pan over medium heat until the onions are soft and translucent.
Add the minced garlic, 1 tbsp of chili powder, 1 tsp of smoked paprika, 2 tbsp of tomato paste, ¼ tsp of salt, and ¼ tsp black pepper to the pan. Add more vegetable broth if it gets too dry. Stir to combine and then let it cook for 2-3 minutes or until fragrant.
Remove the pan from the heat until the sweet potatoes and rice are done cooking. Once everything is ready, add the roasted sweet potatoes, cooked brown rice, and black beans to the pan with the onions. Mix everything together.
Reduce the oven temperature to 350 degrees.
Pour ¼ cup of enchilada sauce into a large casserole dish and spread it around to cover the entire bottom of the casserole dish.
Warm 8 flour or corn tortillas (so they will roll without cracking) and fill each one with a heaping ½ cup of the sweet potato black bean filling. Roll the tortilla up and then place it seam side down into the casserole dish. Repeat until you run out of filling.
Once you’ve squeezed all 8 enchiladas into the dish (it might be a tight squeeze), pour the rest of the enchilada sauce over the top. If you want to add vegan cheese, do it now. Cover the dish with parchment paper and bake it for 25-30 minutes.
Use a thin spatula to get the enchiladas out of the casserole dish. Top each enchilada with thinly sliced romaine lettuce, diced tomatoes, avocado slices, thinly sliced green onions, vegan sour cream, and a drizzle of hot sauce.