Preheat the oven to 450°F and position the oven rack in the center. Line a rimmed baking sheet with aluminum foil for easy cleanup. Place a wire rack on top of the sheet and coat it lightly with vegetable oil spray to prevent sticking.

In a medium-sized bowl, stir together the chili powder, brown sugar, salt, and pepper until well blended. Rub the spice mixture generously over all pieces of chicken, ensuring every surface is well coated. Arrange the seasoned chicken pieces on the prepared wire rack, spacing them evenly. Let the chicken rest at room temperature for 30 minutes, or cover and refrigerate for up to 12 hours to allow the flavors to develop.

Just before roasting, lightly spray the chicken with vegetable oil. Set aside the thinner ends of the split chicken breasts and place the rest of the chicken pieces in the oven. Roast for 10 minutes.

After the initial roasting, add the reserved thinner breast portions to the rack. Continue roasting all the chicken for another 10 minutes.

Rotate the pan in the oven for even cooking. Brush each piece of chicken with half of the barbecue sauce and return to the oven for an additional 10 minutes. Brush with the remaining sauce and roast until the internal temperature of the chicken breasts reaches 160°F—this may take another 10 to 20 minutes depending on your oven and chicken thickness.

Once fully cooked, transfer the chicken to a serving platter and let it rest for 10 minutes to retain its juices. Serve warm with extra barbecue sauce on the side, as desired.