[3] Based at Thirsk with his mother, on reaching his majority in 1138, he took title to the lands awarded to his father by Henry I both in Normandy including Montbray, from which he would adopt his surname, as well as the substantial holdings in Yorkshire and around Melton.
Whilst acknowledged as a competent and prodigious fighter, he generally found himself on the losing side in his subsequent engagements.
[4][5] Roger also had at least one daughter, donating his lands at Granville to the Abbaye aux Dames in Caen when she became a nun there.
[4] Roger supported the Revolt of 1173–74 against Henry II and fought with his sons, Nigel and Robert, but they were defeated at Kinardferry, Kirkby Malzeard and Thirsk.
[2][1] With his mother he sheltered the monks of Calder, fleeing before the Scots in 1138, and supported their establishment at Byland Abbey in 1143.
[7] His cousin William d'Aubigny, 1st Earl of Arundel and his wife Adeliza, the widow of King Henry I, had been amongst the earliest patrons of the order and, when combined with Roger's experiences in the Holy Land, may have encouraged his charity.
[8] His family continued to support the Order for many generations and the Mowbrays lion rampant coat of arms was adopted by the Hospital of Burton St Lazars alongside their more usual green cross.