Preheat oven to 400 degrees F. Place sweet potato cubes on a large baking sheet. Lightly drizzle with olive oil and toss. Season with salt and pepper. Roast in the oven for 40-45 minutes or until sweet potatoes are soft and tender. Stir a couple of times while they are roasting.
In a non-stick skillet, heat corn tortillas over medium-high heat. When tortillas start to bubble up, flip and heat the other side until golden brown, about 30 seconds for each side. Place tortillas on a baking sheet and lightly spray with cooking spray. Place under a hot broiler for about 2 minutes. Remove from oven and turn over tortillas. Place tortillas back under the broiler for another two minutes.
Heat black beans over the stove or in the microwave. Top tortillas with beans, sweet potatoes, onion, cilantro, lime juice, and any other toppings you desire. Serve warm.
*Note-these are a little messy, we just pick them up and eat them with our hands:)