Preheat oven to 425°F. Dice sweet potato and roast for 20 minutes until tender.
Meanwhile, char poblano peppers over open flame or under broiler until skin is blackened. Place in bowl, cover, let steam 10 minutes, then peel and dice.
In a large bowl, combine roasted sweet potato, diced poblanos, red bell pepper, black beans, scallions, serrano (if using), and vegan cheese.
Heat a large skillet over medium heat. Place one tortilla in pan and spread filling evenly over half the tortilla.
Fold tortilla in half and cook 2-3 minutes until golden brown and crispy.
Carefully flip and cook another 2-3 minutes until second side is golden and cheese is melted.
Remove from pan and let cool 1 minute before cutting into wedges.
Repeat with remaining tortillas and filling.