Having checked several printed sources and the general internet for information on the mother of Philippa and Catherine de Roet and/or the wife of Payne de Roet, I have found nothing on her identity. The only sources for Catherine of Hainault being that person are several World Connect data bases-and they do not indicate a source. That does not mean that they are wrong.
Father: William III d' AVESNES , Count of Hainault b: ABT 1286 in Avesnes, Artois/Pas-de-Calais, France
Mother: Jeanne de VALOIS b: ABT 1291 in Valois now Oise, Picardy, France
Marriage 1 Payne de ROET , Sir b: ABT 1315 in Guignies, Hainault, Belgium