Roger de Quincy, 2nd Earl of Winchester (1195? – April 25, 1265) was an English nobleman, and hereditary Constable of Scotland.

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 of Galloway and Margaret of Huntingdon. After the latter's death in 1234, Galloway was divided between the husbands of Alan's three daughters, each receiving a third. The Galwegians rebelled, not wanting their land divided, but the rebellion was suppressed by Alexander II of Scotland. Roger ruled his portion of Galloway strictly, and the Galwegians revolted again in 1247, forcing Roger to hole up in a castle. Faced with a siege and little chance of relief, Roger and a few men fought their way out and rode off to seek help from Alexander, 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, although he fought for Henry against the Welsh in the 1250s and 1260s.

Following Helen's death in 1245, Roger married Maud de Bohun, daughter of Humphrey de Bohun, 2nd Earl of Hereford, around 1250. Maud died only two years later, and Roger married his third wife, Eleanor Ferrers, daughter of William de Ferrers, 5th Earl of Derby the same year.

Roger had three daughters by his first wife, but no sons. His subsequent marriages produced no issue. After his death his estates were divided between the daughters, and the earldom of Winchester lapsed. The three daughters of Roger and Helen of Galloway were:
1. Helen (also known as Ela or Elena), who married Alan Baron Zouche of Ashby;
2. Elizabeth (also known as Isabella), who married Alexander Comyn, 2nd Earl of Buchan;
3. Margaret, who married William de Ferrers, 5th Earl of Derby (and was thus stepmother to her own stepmother).