Preheat the oven to 400 degrees. Peel your sweet potatoes, and chop them into 1-inch chunks. Spread them out on ungreased cookie sheets in a single layer. Roast in the oven for 20 minutes, tossing halfway through.
Meanwhile, prepare the rest of the ingredients. Chop up your garlic, red onion, green chiles and tomatoes.
After 20 minutes, remove the sweet potatoes from the oven and reduce the temperature to 350 degrees.
In a large pan, heat the olive oil over medium-high heat, add the garlic and green chiles and cook for about 30 seconds. Add the black beans, tomatoes, chili powder, salt and pepper.
Stir in the roasted sweet potatoes and let everything cook together for about 5 minutes.
While the filling is on the stove, prepare two 9×13 glass dishes by spraying lightly with olive oil spray, and coating the bottom with a light layer of salsa. Grab your tortillas, and set up a filling station.
Place a spoonful of filling into the middle of each tortilla, roll it up and place it seam-side down in your dish. Repeat until there are eight enchiladas per pan.
Spoon any extra filling over the top. Add 1 cup salsa and half of the chopped red onion to the top of each dish.
Bake the enchiladas for 20 minutes. (At this point I put one in the oven and one in the freezer)
Serve and enjoy!