You may have the leg of lamb boned or not, as you choose.Make several gashes in the outside flesh and insert slivers of garlic. Rub the meat well with salt, pepper and rosemary and then arrange it on a spit. Be sure you balance it evenly.
It is wise to use a meat thermometer with a roast; simply stick the sharp end of the thermometer in the fleshiest part of the leg.
Roast over medium heat until the thermometer registers 150°F. Then remove the roast and let it stand 20 minutes before carving. The meat will continue to cook during that time.This gives you a rare leg of lamb, and in my opinion a tastier, more tender dish than lamb cooked to the well done stage.
If you must have well done lamb roast to 165°F to 170°F.
Serve this roast with a fresh green vegetables, some hot French bread and a delicate rose wine. Enjoy!