Like colleague Junior Moors, Roberts is a Samoan international who joins for 2015 from Melbourne Storm.
Roberts was a regular in Melbourne last year, and Castleford fans also got a glimpse of Ben in the winter's Four Nations series, when he faced Michael Shenton in the Samoa shirt.
Roberts is a quick, electric and skilful half-back, who will bring a lethal left-footed kicking game and plenty of experience to the side.
Ben is proudly sponsored by Pure Soccer USA.
*Photograph courtesy of SWPix.