01 - Set oven to 325°F.
02 - Combine minced garlic, rosemary, thyme, cumin, coriander, paprika, cinnamon, black pepper, salt, lemon zest, lemon juice, and olive oil until a paste forms.
03 - Pat lamb shoulder dry and rub spice paste all over, working it into all surfaces.
04 - Place sliced onions, carrots, and halved garlic bulb in a large roasting pan, then set lamb shoulder on top.
05 - Pour stock and wine (if using) around vegetables in the pan.
06 - Cover pan tightly with foil or lid and roast for 2.5 hours.
07 - Remove cover, increase oven temperature to 400°F, and roast uncovered for 30 minutes until lamb is golden and tender.
08 - Transfer lamb to a board, loosely cover with foil, and rest 15 minutes. Skim excess fat from pan juices and serve alongside lamb and vegetables.