He was the second son of Saer de Quincy, 1st Earl of Winchester, and Margaret de Beaumont. He probably joined his father on the Fifth Crusade in 1219, where the elder de Quincy fell sick and died. His elder brother having died a few years earlier, Roger thus inherited his father's titles and properties. However, he did not take possession of his father's lands until February 1221, probably because he did not return to England from the crusade until then. He did not formally become earl until after the death of his mother in 1235. Roger married Helen, eldest daughter and co-heiress of Alan, Lord of Galloway. After the latter's death in 1234, Galloway was partioned, with Roger and the husbands of his wife's 2 sisters each receiving a third. The Gallwegans rebelled, not wanting their land divi ded. The rebellion was suppressed by Alexander II of Scotland. Roger ruled his portion of Galloway quite strictly, and the Gallwegans revolted again in 1247, forcing Roger to hole up in a castle. Faced with a siege and l ittle chance of relief, Roger and a few men fought their way out and ro de off to seek help from the king, who raised forces to again suppress the rebellion. In the following years Roger was one of the leaders of the baronial opposition to Henry III of England. Roger had 3 daughters, but no sons. After his death his estates were divided between the daughter s, and the earldom of Winchester lapsed. Roger married 3 times. His fir st wife was (as mentioned above) Helen of Galloway, by whom he had the thr ee daughters that became his heiresses. By his last two wives he had no children. The second wife was Maud de Bohun, daughter of Humphrey de Bohun, 2nd Earl of Hereford, and the third wife was Eleanor Ferrers, daughter of William Ferrers, Earl of Derby.
Father: Saher IV De Quincy b: ABT 1155 in Winchester, Hampshire, England
Mother: *Margaret of Harcourt b: ABT 1156 in Hampshire, England
Marriage 1 Maud de Bohun b: ABT 1230 in Flamstead, Hemel Hempstead, Hertfordshire, England
Marriage 2 Eleanor de Ferrers b: ABT 1232 in Derby, Derbyshire, England
Marriage 3 *Helen of Galloway b: ABT 1208 in Wigtownshire, Scotland