The "Scream 4" star is set to portray a character named Madison, who is described as a self-involved party girl. No additional details were made available at this time.
The third season of Ryan Murphy and Brad Falchuk's popular horror miniseries will mark Roberts' return to serial television. The actress' Teen Nick series, "Unfabulous," ended its four year run in 2007.
Earlier this year, she scored the lead role in Karyn Usher's ("Bones," "Prison Break") pilot "Delirium," but Fox opted not to order the show to series.
Roberts will join returning cast members Jessica Lange, Lily Rabe, Sarah Paulson, Frances Conroy, Taissa Farmiga and Roberts' real-life boyfriend, Evan Peters.
TVLine first reported the casting.