Pre-heat the oven to 400 degrees.
Get the brown rice started first because it takes the longest to cook.
While the rice is cooking, start prepping the sweet potatoes. Peel and chop two medium or one large sweet potato.
Arrange the sweet potatoes on a parchment-lined tray and drizzle 1-2 tbsp of vegetable broth (or olive oil) over the potatoes. Sprinkle the chili powder, cumin, garlic powder, onion powder, and smoked paprika over the sweet potatoes. Toss to coat each piece. Bake for 20 minutes.
While the sweet potatoes are roasting, saute 1 diced medium onion in 3 tbsp of low-sodium vegetable broth in a large pan over medium heat until soft, about 8-10 minutes.
Add the minced garlic, 1 tbsp of chili powder, 1 tsp of smoked paprika, 2 tbsp of tomato paste, and 1/4 tsp of salt. Add more vegetable broth if it gets too dry. Saute for 2 minutes.
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. Add a little more vegetable broth if it's too dry. You want the filling to be a little wet but not liquidy. Reduce the oven temperature to 350 degrees.
Pour 1/4 cup of enchilada sauce into a large casserole dish and spread it around to cover the entire bottom of the casserole dish. (If you skip this step, the enchiladas will stick to the casserole dish.)
Warm 8 flour or corn tortillas (so they will roll without cracking) and fill each one with a heaping 1/2 cup of the sweet potato black bean filling. Roll the tortilla snugly and place it seam side down into the casserole dish. Repeat until you fill all 8 enchiladas.
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 or green leaf lettuce, diced tomatoes, sliced avocado, sliced green onions, vegan sour cream, and a drizzle of hot sauce.