Step 1: Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Step 2: In a large bowl, toss the cubed sweet potatoes with olive oil, cumin, smoked paprika, chili powder, garlic powder, salt, and pepper until evenly coated.
Step 3: Spread the sweet potatoes in a single layer on the prepared baking sheet and roast for 25-30 minutes, or until they are tender and the edges are golden brown.
Step 4: While the potatoes roast, place the drained black beans in a small saucepan over medium-low heat. Add a splash of water or lime juice and warm through for about 5 minutes.
Step 5: Warm the tortillas in a dry skillet over medium heat for 30 seconds per side until soft and pliable.
Step 6: To assemble the sweet potato and black bean tacos, place a generous spoonful of roasted sweet potatoes and black beans onto each tortilla.
Step 7: Top with avocado slices, cilantro, diced red onions, and a squeeze of fresh lime juice before serving immediately.