01 - Preheat the oven to 325°F.
02 - In a small bowl, combine olive oil, salt, pepper, garlic, rosemary, thyme, oregano, lemon zest, and lemon juice to create a herb paste.
03 - Pat the lamb shoulder dry with paper towels. Rub the herb paste thoroughly over the lamb, making sure to get into any crevices.
04 - Arrange the 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 or chicken broth into the pan around the lamb, not over it.
06 - Cover the pan tightly with foil. Roast in the preheated oven for 2½ hours.
07 - Remove the foil and increase the oven temperature to 400°F. Continue roasting for another 30 minutes, or until the lamb is well browned and the meat is tender and pulls away easily from the bone.
08 - Remove from the oven and let rest, loosely covered with foil, for 15 minutes before carving.
09 - Serve with pan juices and roasted vegetables.