1.Preheat oven to 200°C (180°C fan-forced).
2.Combine couscous with the water in medium heatproof bowl, cover; stand about 5 minutes or until water is absorbed, fluffing with fork occasionally. Toss prunes, nuts, coriander and parsley into couscous.
3.Remove excess fat from pork. Place pork on board, upside-down; slice through thickest part of pork horizontally, without cutting through at the other side. Open pork out to form one large piece; press 1 cup of the couscous mixture against loin along width of pork. Roll pork to enclose stuffing, securing with kitchen string at 2cm intervals.
4.Place rolled pork on rack in large shallow flameproof baking dish; pour 2 cups of cider over pork. Roast, uncovered, about 50 minutes or until cooked through. Remove pork from baking dish; cover to keep warm.
5.Place remaining couscous mixture in small ovenproof dish; cook, covered, about 10 minutes or until heated through.
6.Meanwhile, heat pan juices in baking dish on top of stove; add remaining cider, apple, onion and sugar. Cook, stirring, until apple is just tender. Serve sliced pork with apple mixture and couscous.