"Jason is a natural goalscorer, I can't really put it any other way," said Latics boss Roberto Martinez.
"Every manager wants a player who has that clinical ability to make something happen in the box, and Jason can do that.
"He is strong, very physical, and his feet can produce the magic ingredient every team needs in the box.
"This was always going to be a key signing for me.
"I have every faith he can make the step up to the Premier League and become a real cult hero at the Latics.
"I know from experience how the Wigan fans love a goalscorer. Graeme Jones, Andy Liddell, Nathan Ellington, Jason Roberts.
"I am confident Jason can be the next name on that list."