01 - Preheat the oven to 320°F.
02 - In a small bowl, combine minced garlic, chopped rosemary, sea salt, black pepper, olive oil, lemon zest, and lemon juice until paste forms.
03 - Pat the lamb shoulder dry and thoroughly rub the marinade all over the surface.
04 - Place sliced onions, carrots, and celery in a large roasting pan, creating a bed for the lamb.
05 - Set the lamb shoulder atop the vegetables in the roasting pan.
06 - Pour white wine and stock around the lamb, avoiding pouring directly over it.
07 - Cover the roasting pan tightly with foil or a lid and roast in the oven at 320°F for 3 hours.
08 - Remove the cover, increase the oven temperature to 400°F, and roast uncovered for an additional 30 minutes to brown the lamb.
09 - Let the lamb rest for 15 minutes before carving. Serve alongside the roasted vegetables and pan juices.