|Died||In 5 AC, Sunspear|
Jon Rosby was the Lord of Rosby and the head of House Rosby during the early reign of King Aegon I Targaryen.
During the First Dornish War, after capturing the major strongholds of the Dornish nobility, King Aegon I Targaryen marched upon House Martell's seat of Sunspear. Upon finding it half-deserted and the Martells absent, Aegon declared victory and informed the remaining Dornish dignitaries that they were now part of the Seven Kingdoms. Lord Jon Rosby was named Castellan of Sunspear and Warden of the Sands to rule Dorne in the king's name, while stewards and castellans were named for other castles and lands. Soon after, Aegon and his host departed Dorne. While ruling from Sunspear, Rosby was to be supported by Lord Harlen Tyrell's garrison at the Hellholt.
When the Dornishmen soon returned from the shadow city, Rosby was quickly bound and captured. While Aegon's other castellans and stewards were tortured, Rosby had a kinder end than most in the resulting Defenestration of Sunspear, with the aged Princess Meria Martell throwing him from the top of the Spear Tower. Lord Tyrell set out from Hellholt with his host to avenge Rosby, but disappeared soon after in 5 AC.