Preheat your oven to 400°F (200°C). Line the sheet pan with parchment paper for easy cleanup, if desired.
In a mixing bowl, combine the diced bell peppers, onion, corn, olive oil, cumin, chili powder, salt, and black pepper. Toss the ingredients until well coated.
Spread the vegetable mixture evenly on the sheet pan and roast in the preheated oven for about 10 minutes or until the vegetables are tender.
Remove the sheet pan from the oven and reduce the temperature to 375°F (190°C).
On half of each tortilla, sprinkle an even layer of shredded cheese, followed by a layer of the roasted vegetable mixture and a portion of the shredded chicken (or black beans). Top each with another layer of cheese.
Fold the other half of the tortilla over the filling, pressing down gently to secure. Repeat this process for all tortillas.
Place the filled quesadillas on the sheet pan and bake for 10-12 minutes, flipping them halfway through, until the cheese is melted and the tortillas are golden and crispy.
Remove the quesadillas from the oven and let them cool for a few minutes. Cut each into wedges and serve with your favorite toppings such as salsa, guacamole, or sour cream.