01 - Preheat the oven to 325°F.
02 - Pat the lamb shoulder dry with paper towels. Rub all over with olive oil, salt, and black pepper.
03 - In a small bowl, combine garlic, rosemary, thyme, parsley, oregano, lemon zest, and red pepper flakes. Press the herb mixture over the lamb, coating it evenly.
04 - Scatter onions, carrots, and celery in the bottom of a large roasting pan. Place the lamb shoulder on top of the vegetables.
05 - Pour the white wine and broth into the pan around (not over) the lamb.
06 - Cover tightly with foil or a lid and roast for 2 hours.
07 - Remove the foil or lid, increase oven temperature to 400°F, and roast for an additional 30 minutes to brown the top and crisp the edges.
08 - Remove from oven, tent with foil, and let rest for 15 minutes before carving. Serve with roasted vegetables and pan juices.