Preheat your oven to 400°F (200°C).
In a large bowl, toss the diced sweet potatoes with olive oil, chili powder, cumin, salt, and pepper until evenly coated.
Spread the seasoned sweet potatoes in a single layer on a baking sheet. Roast in the preheated oven for 20-25 minutes, or until tender and lightly browned, stirring halfway through cooking.
While the sweet potatoes are roasting, prepare the black bean and corn filling. In a skillet, heat a little olive oil over medium heat. Add the diced red onion and cook until softened, about 3-4 minutes.
Add the minced garlic and diced jalapeño (if using) to the skillet and cook for another 1-2 minutes, until fragrant.
Stir in the black beans and corn kernels. Cook for 5-7 minutes, or until heated through. Season with salt and pepper to taste.
Remove the skillet from heat and stir in the chopped cilantro and lime juice.
Warm the tortillas according to package instructions.
To assemble the tacos, spoon some of the roasted sweet potatoes onto each tortilla, followed by the black bean and corn filling.
Add desired toppings such as sliced avocado, shredded lettuce or cabbage, diced tomato, salsa, Greek yogurt or sour cream, and hot sauce.
Serve immediately and enjoy your Sweet Potato and Black Bean Tacos!