When buying your roast, ask the butcher to saw across the rib bones at the base of the backbone, to separate the ribs from the backbone.
Place the roast in a large ziplock bag. Pour the brandy over the roast; seal the bag. Place the bag in a large bowl; marinate in the refrigerator 4 hours, turning occasionally.
Remove the roast from the marinade, reserving the marinade. Set the marinade aside. Combine the salt and the next 4 ingredients; rub the spice mixture over the entire surface of the roast. Place roast, fat side up, on a rack in a shallow roasting pan; insert a meat thermometer, making sure it does not touch fat or bone. Bake at 325 degrees for 2 hours.
Place the potatoes in a large saucepan; add water to cover. Bring to a boil; cover, reduce heat, and simmer 5 minutes. Drain; quarter potatoes and set aside.
Remove the roast and rack from the roasting pan; set aside. Discard the pan drippings. Place the apple slices in the center of the roasting pan; sprinkle with brown sugar and cinnamon.
Strain the reserved marinade through several layers of cheesecloth. Place the marinade in a small, long handled saucepan. Bring to a boil; reduce heat, and simmer 3 minutes. Remove from the heat and ignite; pour over apples. Let the flames die down.
Place the reserved potatoes around the apples in the roasting pan. Place the roast on top of the apples. Bake at 350 degrees for 45 minutes or until the meat thermometer registers 160 degrees, turning the potatoes after 30 minutes.
Remove the roast and apples from the pan; place on a serving platter. Increase the oven temperature to 500 degrees; bake the potatoes for 5 minutes. Arrange the potatoes around the roast. Let roast stand 10 minutes before serving.