Bring lamb to room temperature. Heat oven to 325. Roast lamb for 1 hour (30 minutes for a smaller leg). Drain off any fat. Put hot water into the pan. Continue to roast lamb, basting every 20 minutes, first with remaining basting mixture, then with juices in the pan. Allow 20 minutes per pound, or until meat thermometer registers 140 for rare, 160 for medium, or 170 for well done. Remove from oven, cover lightly with foil and allow meat to rest 20 minutes before carving. Skim fat from juices and serve pan drippings with the lamb.