|Title||Lord of Rosby|
|Died||In 130 AC, King's Landing|
Dance of the Dragons
During the reign of King Viserys I Targaryen, Lord Rosby swore to defend the succession rights of Princess Rhaenyra Targaryen. In 129 AC, during the Dance of the Dragons in which Rhaenyra's brother Aegon II Targaryen challenged her rule by claiming Viserys's throne for himself, Lord Rosby was arrested by Aegon II's supporters. When given the choice between swearing his allegiance to Aegon II or being killed by the King's Justice, Lord Rosby pledged his support to Aegon II.
When Ser Criston Cole marched from King's Landing to attack Duskendale and ultimately Rook's Rest, he passed by Rosby and Stokeworth to command both Lord Rosby and Lord Stokeworth to prove their loyalty by joining his attack. When King's Landing fell to Queen Rhaenyra during 130 AC, Lord Rosby attempted to switch his allegiance again. However, Queen Rhaenyra refused him, saying that faithless friends were worse than foes. She ordered his "lying tongue" removed, after which he was executed.
Lord Rosby left behind at least two children, including a twelve-year-old daughter and a younger son. Prince Daemon Targaryen suggested marrying Rosby's young daughter to Hugh Hammer, to grant Hammer the Rosby lands. Lord Corlys Velaryon, the Hand of the Queen, argued instead that Rosby's younger son should receive the inheritance. According to Lord Corlys, Rhaenyra's case was special, as King Viserys had named her as his heir, but Lord Rosby had never done so. Disinheriting the younger son in favor of the older daughter would call into question the rights of multiple other lords, who had elder sisters whose claims might suddenly be seen as superior. According to Grand Maester Munkun, Rhaenyra was unwilling to lose the support of such lords, and named Rosby's son as the new Lord of Rosby.
Later in 130 AC, riots in King's Landing led Queen Rhaenyra to abandon the city and flee to Dragonstone. On the way, she found Rosby's castle gates barred at her approach, by the command of the late Lord Rosby's daughter, whose claim Rhaenyra had passed over in favor of her younger brother.
Blood of Dragons
In the approved on-line roleplaying game Blood of Dragons created by Elio García and Linda Antonsson, he is given the name "Mathar Rosby", and a few more details about the fate of his family are given. However, these details are not considered canonical, and are provided on this article for informational purposes only.