Preheat the oven to 400 degrees Place the sweet potatoes on a large baking sheet. Drizzle with olive oil and toss.
In a small bowl, combine the chili powder, salt, cumin, smoked paprika, garlic powder, and black pepper. Sprinkle the seasonings over the sweet potatoes and toss until potatoes are well coated. Place the pan in the oven and roast for 25 to 30 minutes, stirring once, or until potatoes are tender.
While the sweet potatoes are roasting, make the slaw. In a medium bowl, combine the shredded Brussels sprouts, shredded cabbage, green onion, cilantro, lime juice, chili powder, cumin, salt, and pepper. Toss well.
To assemble the tacos, top corn tortillas with the roasted sweet potatoes, black beans, slaw, avocado, a drizzle of creamy cilantro lime dressing, a sprinkle of queso fresco, and pepitas. Serve immediately.