Rotrou took part in the First Crusade, travelling with the army of Robert Curthose, Duke of Normandy. What influenced Rotrou in this regard were probably familial connexions. He was related to the Anglo-Norman aristocracy and the Perche was a march (border region) in southern Normandy. A sister was married to Raymond of Turenne, who was a fellow Crusader in the following of Raymond IV of Toulouse. His mother, Beatrix, was a sister of Ebles II of Roucy, who had campaigned in Spain in 1073, and Felicia, who married Sancho Ramírez, King of Aragon. A religious motivation cannot be discounted.