The night before grilling, mix together the olive oil, wine, rosemary, and garlic in a small bowl.
Place the leg of lamb roasts in a dish or plastic storage bags.
Pour the marinade over the roasts and place them in the refrigerator to season overnight.
The next day, light the grill and heat to a low heat. I use a Big Green Egg and let it heat to about 300°.
Place a baking stone or cookie sheet on the grill rack. Then place the V-shaped roasting rack on the stone or sheet. This will smoke and roast the meat with diffused heat.
Place the roasts in the V-shaped rack and close the lid on the grill. Watch the temperature and keep it steady at about 300°.
Roast the lamb for about 1½ hours until medium rare. If the doneness indicators in the roast don't pop up, that's good. Lamb is best when served medium-rare and no more than medium.
After about 1½ hours, remove the lamb roasts from the fire and place them in a shallow pan or on a platter to rest. Let them rest for about 10 minutes to allow the juices to distribute throughout the meat.
Slice it thin and serve.