First, the Battle Abbey Roll is a notoriously inaccurate source. The only member of the de Grenville family named Robert who came over during this time period was Robert fitz Hamon. But he and his brother Richard de Grenville (progenitor of the de Grenville family in England who later were Dukes of Buckingham) came to England after the conquest. Robert served William Rufus, and later Henry I. He died in 1107 from wounds received in Normandy. His daughter Mabel married Henry I's natural son, Robert de Caen, Earl of Gloucester. Could this be who you are referring to?

JL