01 - Preheat the oven to 300°F.
02 - Combine olive oil, melted butter, sage, garlic, lemon juice, lemon zest, salt, and pepper in a small bowl.
03 - Pat turkey legs dry with paper towels and rub the marinade generously over each leg for thorough coverage.
04 - Place sliced onion, carrots, and celery evenly in a large roasting pan. Position the turkey legs on top of the vegetables and pour broth around (not over) the legs.
05 - Cover the pan tightly with aluminum foil and roast for 2 hours, basting the turkey legs with pan juices halfway through.
06 - Remove the foil, increase oven temperature to 400°F, and roast uncovered for 15 minutes until skin is golden and crisp.
07 - Allow the turkey legs to rest for 5 to 10 minutes before serving. Spoon pan juices and vegetables over each portion.