Heat your wood-fired oven 2 hours before cooking. You want it to be a medium-high heat, about 400 degrees F.
Add the olive oil, rosemary, salt, pepper, garlic, lemon juice and zest in a mortar and pestle and smash until it reaches a paste. Place the lamb on a sheet tray and rub the paste all over the lamb, getting into every inch of space. If time allows, you can marinate the lamb for at least 4 hours or overnight.
Place the lamb on a sheet tray or roasting pan outfitted with a wire rack. Put in the oven and roast until the lamb reaches an internal temperature of 145 degrees F, about 1 1/2 hours.
Allow the lamb to rest for 20 minutes for the juices to redistribute before carving. Carve against the grain, using the bone as a handle. Place the slices on a platter and garnish with rosemary sprigs and lemon zest. Serve with a simple arugula salad.