Season lamb with sea salt, pepper and rosemary leaves and place in a deep dish. To prepare the marinade, blend all ingredients in a small bowl and pour over the lamb. Cover and refrigerate, preferably overnight. Turn over at least twice.
Preheat oven to 180°C. Place pan uncovered in the oven and roast one side for 1 hour or until lamb turns golden brown. Turn over and roast other side for 1 hour.
If marinade evaporates while baking, add water and wine to keep roast from sticking to the bottom of the pan and becoming too dry. When ready remove from pan, set aside for 10 minutes and thinly slice.
Serve the Mandarin Marmalade Sweet Roasted Leg of Lamb with roasted young potatoes, sea salt, extra virgin olive oil and any of the salads featured here.