Preheat oven to 325 degrees, melt butter in roasting pan.
Combine salt, pepper, chili powder, cumin and oregano and sprinkle over both sides of chicken thighs, pressing into meat and skin.
Place chicken skin side down in roasting pan with melted butter. Cover tightly with foil and roast for an hour.
Remove pan from oven, remove foil and turn chicken thighs skin side up. Roast uncovered for an additional 25-30 minutes.
Turn broiler on high and broil for 2-3 minutes until skin is crispy and golden.