Background
He was the son of Hugh de Mortimer (d 26 February 1181) and Matilda Le Meschin.
He was the son of Hugh de Mortimer (d 26 February 1181) and Matilda Le Meschin.
In 1179 Roger was instrumental in the killing of Cadwallon ap Madog, the prince of Maelienydd and Elfael, both of which Mortimer coveted. He was imprisoned until June 1182 at Winchester for this killing. In 1195 Roger, with the backing of troops sent by King Richard I invaded Maelienydd and rebuilt Cymaron Castle.
In 1196 he joined forces with Hugh de Say of Richards Castle and fought and lost the battle of New Radnor against Rhys ap Gruffydd, allegedly losing some forty knights and an innumerable number of foot in the fight.
By 1200 he had conquered Maelienydd and issued a new charter of rights to Cwmhir Abbey. He died before 8 July 1214.