Put 4 cups of wood chips to soak in water for at least one hour prior to smoking your lamb.
Remove the netting from around your lamb shoulder roast, rinse it under cold running water and pat it real dry. Lay it flat on a cutting board (slice open the thicker parts if necessary) and make several deep incisions throughout the roast with a paring knife. Insert pieces of fresh rosemary into those incisions. Sprinkle generously with salt and pepper.
Preheat your outdoor grill to 225°F. Turning on a single burner on the lowest setting should do the trick.
Make 8 wood chip pouches. For each pouch, cut out a 12” x 24”piece of heavy duty aluminum foil (double that up if using lighter foil) and place about half a cup of wet wood chips on one end of the foil. Add a handful of dry chips to that, then fold the foil over the wood chips. Fold all four edges toward the center at least twice, then poke holes on the top and bottom of the pouch with a fork or other sharp object.
Lift the grill that’s above the lit element and place 2 pouches directly on the heat source. Close the lid and wait until smoke starts to come out of the pouches.
Place your lamb roast on the unlit side of the grill and close the lid.
Smoke the meat for about 6 hours, replacing the pouches with 2 fresh ones every 90 minutes or so. If necessary, crank up the heat under the new pouch until smoke starts to come out then bring the heat back down to low.
Try and keep the heat inside your grill as stable as possible, at around 225°F. Note that it’s not necessary to get huge amounts of smoke in order to get good flavor from it. However, if you feel you are not getting enough, feel free to add more dry chips to your foil pouches, or place an aluminum container with a handful of dry chips next to your existing foil pouches.
After the lamb has smoked for 6 hours, remove it from the grill and wrap it in aluminum foil. Use a double layer to make sure none of the cooking juices leak out. You want to preserve moisture in this time.
Place it back on the grill and crank up the heat to 350°F. Cook the meat for an additional 90 minutes, or until the meat gets real tender and can easily be pulled with a fork.
Remove the roast from the grill and let it rest for 10 minutes, then carve and serve drizzled with some of the cooking juices.