Variety reports that this job entails "overseeing the writing on the titles, working with executive producers and writers to help develop story arcs and helping to digest the book series' 10,000 pages and over 1,700 characters."
(Of course, Morgan and the other two screenplay writers, Derek Haas and Michael Brandt, were taken to task by fans for not sticking to the original comic book story all that much. However, compared to comic book purists, the wrath of Robert Jordan fans can be deadly. Or so I hear.)
Morgan isn't the only screenwriter who has dipped his toes into the pixellated pool. Saw director James Wan is one of the writers for the Saw video game, which surprisingly got some good gamer feedback from its preview at SDCC. And David McKenna, who wrote American History X, Get Carter, Blow, and Bully, wrote Scarface: The World is Yours, which got generally mixed reviews.