Preheat the oven to 400°F (200°C). Line a baking sheet with foil and place a baking rack on top; lightly spray the rack with nonstick cooking spray.
Pat the chicken thighs dry with paper towels and arrange them skin-side up on the prepared rack. Let rest at room temperature for 20 minutes.
In a medium bowl, combine baking powder, paprika, garlic powder, chili powder, onion powder, salt, brown sugar, dried oregano, dried basil, black pepper, dried thyme, and ground cumin; whisk to make the spice rub.
Drizzle a small amount of olive oil over each thigh and rub to coat both sides. Turn thighs skin-side-down briefly to oil the underside.
Sprinkle half of the spice rub over the top of the chicken and gently pat it in. Flip the thighs skin-side up, sprinkle with the remaining rub, and pat again.
Roast the chicken in the preheated oven without flipping until the thickest part of the thigh (not touching bone) reaches 170°F (about 35–45 minutes, depending on size).
Optional: For extra crispy skin, broil on high for 1–2 minutes, watching closely to avoid burning.