Per Weis' "Ancestral Roots. . ." (89:29), (208:29), (215:29, 1st Baron Ros of Helmsley and Belvoir, Leicestershire., M.P. 1261, 1265. According to Cockayne's "Complete Peerage", in 1258 he was appointed chief commissioner of Herfordshire to inquire into excesses there. In that same year he was summoned for service against the Welsh and the Scots. He sided with Simon de Montfort in 1264/4 and was holding Northampton under the younger Simon when the King took it. He was summoned to Montfort's parliament. In 1265 Prince Edward (The future King Edward I) escaped from his custody at Hereford. Robert later surrendered Gloucester Castle to the Prince. After Montfort was slain and his rebellion quashed at the Battle of Eversham Robert received a full pardon at the insistence of Prince Edward. In 1276 he was one of the magnates, who, in council at Westminster, gave judgement against Llewelyn, and was summoned for service in the consequent campaign. By his marriage he became Lord of Belvoir.