Nothing is known of his background or his early life. His appointment to the office of Serjeant was probably made in 1261. The title Serjeant-at-law was not then in use in either England or Ireland: he was called King's Serjeant or, less often, King's Pleader, while Roger himself used the Latin title of "serviens". In a letter to King Edward I of England in 1275, he described his work as being to "prosecute and defend the King's pleas in Ireland".
