01 - Preheat the oven to 425°F and line a baking sheet with parchment paper.
02 - In a large bowl, toss diced sweet potatoes, sliced onion, and chopped bell pepper with olive oil, cumin, smoked paprika, chili powder, coriander, salt, and black pepper until evenly coated.
03 - Spread the vegetable mixture evenly on the baking sheet and roast for 25 to 30 minutes, turning halfway through, until tender and caramelized. Let cool for 5 minutes.
04 - Heat a large skillet over medium heat, add minced garlic and black beans, and cook for 2 to 3 minutes, stirring occasionally until warmed through.
05 - Warm tortillas in a dry skillet or microwave until pliable.
06 - Lay each tortilla flat and layer roasted vegetables, black beans, shredded cheese if using, avocado slices, and a spoonful of sour cream or Greek yogurt. Sprinkle with chopped cilantro.
07 - Fold the sides of the tortilla inward and roll tightly to enclose fillings.
08 - Place burritos seam-side down in a skillet over medium heat and toast for 2 to 3 minutes per side until golden and crisp.
09 - Serve the burritos hot, accompanied by lime wedges.