Same happened to me, it didn't auto-populate the remainder of the roster and then wouldn't let me continue because even after I filled as much of the roster as possible they only gave me 4 starting pitchers and it wouldn't let me start without the starting rotation completed... i'm sure it would have complained about the relievers also, as they also didn't provide enough relievers to fill all the spots so I had to forfeit.
Same as the other posters, the Finest Showdown in Other Programs that's required to get the Gagne, Delgado, and Carter Finest cards.