Preheat your oven to 400°F (200°C). Spread the diced sweet potatoes on a baking sheet, drizzle with olive oil, and season with salt, pepper, cumin, and chili powder. Toss well to coat and roast for about 20 minutes or until tender and slightly caramelized.

While the sweet potatoes are roasting, heat a little olive oil in a skillet over medium heat. Add the chopped onion, and sauté until translucent (around 5 minutes). Then, stir in the minced garlic and cook for an additional minute until fragrant.

In a large mixing bowl, combine the roasted sweet potatoes, sautéed onions and garlic, and black beans. Stir gently to mix all the ingredients.

Lay one tortilla flat on a clean surface. Sprinkle a little cheese on one half, spoon some of the sweet potato mixture over the cheese, and top with a bit more cheese. Fold the tortilla in half to cover the filling.

Wipe down the skillet and add a splash of olive oil over low to medium heat. Cook the folded quesadilla for about 3-4 minutes on each side or until the exterior is golden and crispy. Repeat the process for the remaining tortillas.

Slice the quesadillas into triangles, optionally garnishing with fresh cilantro. Serve warm with your favorite dipping sauce or toppings.