Roberts looked set to join the Latics but now seems set to sign for Portsmouth on a season long loan deal as they use him to keep in the Premiership.
Roberts has preferred partnering old man Sheringham at Pompey to Nathan Ellington at the Latics in a strike force for the rest of the season.
Pompey chief executive Peter Storrie told the club's official website: "I contacted the West Bromwich Albion chairman on Friday night and thrashed out a deal.
"Jason is a proven scorer who gives us another option up front and we are very pleased to have him."
This is a big disappointment to the club.
