Take the roast out of the refrigerator 15 minutes before cooking.
Preheat oven to 375°F (190°C).
Melt the duck fat in an oven-safe pan. Take the roast out of the packaging, rinse under cold water and pat dry with paper towel and place in the roasting pan. Sear the roast over high heat to brown the skin, a few minutes on each side. Place it in a roasting pan, and cook for 45 minutes in the oven. Cooking times may vary depending on the type of oven used. Duck roast is best when the meat is pink, with an internal temperature of 145°F (63°C). Remove the roast from oven and let rest for 10 minutes, loosely covered with aluminium foil.
Meanwhile, reduce duck stock to 2/3. Deglaze with wine and reduce to half. Add the cherry and prune jam, mixing well. Add the sprig of rosemary. Simmer for a few minutes until desired consistency is reached. Season to taste.
Slice the roast and coat with sauce.
