Pat the lamb dry, arrange it, boned side up, on a work surface, and season it with salt and pepper. Rub with 2 tablespoons of oil. Spread the lamb evenly with the olive-cheese-tomato mixture, leaving a 1-inch border around the edges. Beginning with a short side, roll it up jelly roll fashion, and tie it tightly with kitchen string. The rolled and tied roast may look ungainly, but it will improve in appearance when cooked.
Transfer the lamb to a roasting pan and rub it all over with the remaining 1 tablespoon of oil, 1 teaspoon rosemary and salt and pepper to taste. Roast the lamb in the middle of a preheated 325 degree oven for 30 minutes, scatter the onion around it in the pan, and roast the lamb for 1 to 1 1/4 hours more (a total of 20 minutes per pound of boneless meat ) or until a meat thermometer registers 140 degrees for medium rare. Transfer the lamb to a cutting board and let it stand for 20 minutes.
While the lamb is standing, skim the fat from the pan drippings and set the roasting pan over moderately high heat. Add the wine, deglaze the pan, scraping up the brown bits, and boil the mixture until it is reduced by half. Strain the mixture through a fine sieve into a saucepan, add the broth, the remaining 1/2 teaspoon rosemary, the water, and any juices on the cutting board. Boil the mixture until it is reduced to about 2 cups. Stir the cornstarch mixture, add it to the wine mixture, whisking, and simmer the sauce for 2 minutes. Season the sauce with salt and pepper and keep it warm.
Discard the lamb strings. Slice and arrange on a heated platter. Surround with quinoa timbales and clusters of the carrots. Strain the sauce into a heated sauceboat and serve with the lamb
Recipe Courtesy of Gourmet Magazine