For the Stuffing
Heat one tablespoon of oil in a frying pan on low heat. Add onions, garlic, and salt and cook until softened, about 10 minutes. Add pine nuts and raisins and cook for one minute. Add honey and red wine vinegar. Remove from heat and allow to cool.
Pick and chop the leaves from the parsley, thyme, and rosemary. Place in a food processor and blend while slowly pouring in the remaining oil. Add the Pecorino, pulse a few times, then add the breadcrumbs, pulsing again until the mixture just comes together. Remove from processor and combine with cooled pine nut mixture. Check seasoning.
For the Lamb
Preheat oven to 180⁰C
Remove lamb from the refrigerator two hours before cooking to allow it to warm to room temperature. Season well.
Place deboned lamb on a chopping board, fat side down. Place stuffing in the middle along the whole length inside the lamb. Roll lamb from one side to the other. Tie along the length of the rolled-up leg with string, at three-centimeter intervals. Rub with oil and put in a large roasting tin. Cook for 30 minutes, then reduce temperature to 160⁰C. After about 40 more minutes, start checking the core temperature of the meat. Continue to roast until it reaches 55~56⁰C. Let sit for 30 minutes.
For the Sauce
In a saucepan, over medium-high heat, add the olive oil. When the oil is hot, add the onions and sauté until translucent. Add the tomatoes, rosemary, and parsley. Then, add the Demi-Glace.
Reduce the sauce. Once the sauce has reduced, remove from heat and pass through a strainer. Return the sauce to the pan and stir in butter to finish.
Remove the string from the lamb, slice, and serve along with any juices from the roasting pan and the rosemary sauce.