Place chopped onions and sweet potatoes in a single layer on a rimmed sheet pan. Drizzle with olive oil, spices and salt and pepper. Toss to evenly distribute oil and spices over the vegetables. Place in a 425 degree oven for 15 minutes, then toss veggies with a spatula and return to oven for another 10-15 minute, until veggies are cooked through and starting to caramelize.
Add the drained black beans to the onion and sweet potatoes on the sheet pan. Toss gently to combine and place back in the oven for five minutes to warm up the beans.
Place bean and vegetable mixture into a warm tortilla and garnish as desired.