Actually, according to http://www.newadvent.org/cathen/13098c.htm
he was martyred on Dec. 10th. And "In 1970, John Roberts was canonized by Pope Paul VI as one of the Forty Martyrs of England and Wales, whose joint feastday is kept on 25 October."

This site also has a link to costumes so you can "dress up as a Religious character" (that's what it says!).