Heat the oven: Preheat to 425°F (220°C). Lightly oil a sheet pan.
Roast the sweet potatoes: Toss the diced sweet potatoes with 1/2 tablespoon olive oil, a pinch of salt, and pepper.
Spread on the sheet pan and roast for 18–22 minutes, stirring halfway, until tender and caramelized at the edges.
Sauté aromatics: While the potatoes roast, heat the remaining 1/2 tablespoon olive oil in a skillet over medium heat. Add onion and bell pepper; cook 5–6 minutes until softened. Stir in garlic for 30 seconds.
Season the filling: Add cumin, chili powder, smoked paprika, oregano, salt, and pepper.
Stir to bloom the spices for 30 seconds.
Add beans and sweet potatoes: Fold in the black beans and roasted sweet potatoes. Warm through for 1–2 minutes. Taste and adjust salt.
Stir in cilantro if using. Remove from heat.
Prep the baking dish: Reduce oven to 375°F (190°C). Lightly oil a 9x13-inch baking dish.
Spread a thin layer (about 1/2 cup) of enchilada sauce on the bottom.
Soften tortillas: Warm tortillas so they’re pliable. Microwave them wrapped in a damp towel for 30–45 seconds, or quickly toast each side in a dry skillet.
Fill and roll: Place 2–3 tablespoons of filling down the center of each tortilla. Add a small sprinkle of cheese.
Roll snugly and place seam-side down in the baking dish.
Sauce and cheese: Pour the remaining enchilada sauce evenly over the rolled tortillas. Top with the remaining cheese.
Bake: Bake uncovered for 15–20 minutes, until the cheese is melted and the sauce is bubbling at the edges.
Finish and serve: Let rest 5 minutes. Add toppings like avocado, jalapeños, more cilantro, and a squeeze of lime.
Serve warm.