|Title(s)||Lord of Rosby|
|Died||In 130 AC, King's Landing|
The World of Ice and Fire (mentioned)|
Fire and Blood (mentioned)
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. Queen Rhaenyra refused him, however, and ordered his tongue removed, after which he was executed.
Following Lord Rosby's death, 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 in favor of Rosby's younger son. According to Lord Corlys, 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. Unwilling to lose the support of such lords, according to Grand Maester Munkun, Rhaenyra eventually named Rosby's son as the new Lord of Rosby.
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.