According to Michael Ausiello at EW, Duff will play the new NYU roommate for Jessica Szohr's Vanessa and that the character will make her first appearance in the season's fourth episode, airing on October 5.
The good folks at E! have additional information on Duff's character, whose name will be Olivia. Their sources say that Olivia is a movie star trying to go to school incognito and that she'll be a potential love interest for Penn Badgley's Dan.
Most recently seen on the big screen in "War Inc." and "Material Girls," the "Lizzie McGuire" star's latest small screen appearances have been on episodes of "The Ghost Whisperer" and "Law & Order: Special Victims Unit."