In a large zip top bag, mix together honey, garlic, dijon, rosemary, lemon juice, oregano, pepper, and salt. Add lamb to the zip top and massage to coat all sides of lamb leg. Remove air from the bag, seal, and marinate lamb for 8 hours or overnight.
Preheat smoker to 250°F.
Meanwhile, remove lamb from refrigerator and rest for one hour at room temperature. Discard marinade.
Roll lamb roast together (in a round shape) and place on the grate. Smoke lamb until it reaches 135°F using a digital thermometer, approximately 2-3 hours.
Remove lamb from smoker and rest uncovered for 10 minutes.
Sear in a cast iron skillet until internal temperature reaches 140°F on a digital thermometer. Alternatively, broil in the oven, watching carefully, until the lamb's internal temperature reaches 140°F.
Rest lamb uncovered for 15 minutes. Slice and serve.