01 - Preheat the oven to 300°F.
02 - Combine olive oil, melted butter, sage, garlic, lemon juice, lemon zest, salt, and black pepper in a small bowl to form the marinade.
03 - Pat turkey legs dry using paper towels. Generously rub the marinade over each leg ensuring even coverage.
04 - Lay sliced onion, carrots, and celery evenly in the bottom of a large roasting pan. Place turkey legs on top, then pour broth around them without drenching the meat.
05 - Cover the roasting pan tightly with aluminum foil and roast for 2 hours, basting turkey legs once halfway through cooking.
06 - Remove the foil, increase oven temperature to 400°F, and roast uncovered for 15 minutes until skin is golden and crisp.
07 - Allow turkey legs to rest for 5 to 10 minutes before serving. Spoon pan juices and vegetables over each portion.