Rossum will play Ridley, a cousin who becomes a dark witch and becomes an enemy to the protagonist.
The film is based off the young adult fantasy book by Kami Garcia and Margaret Stohl of the “Beautiful Creatures” series.
The plotline follows the character Lena Duchannes hiding her powers from the Southern town of Gatlin and her relationship with a local boy Ethan Wate.
Other cast members already included Jack O’Connell, Alice Englert, Viola Davis and Emma Thompson.
The film has a 2013 realease date with a production start date next month.
Rossum currently stars in the Showtime’s television series “Shameless” with William H. Macy. Her past film credits included “The Day After Tomorrow,” “The Phantom of the Opera,” “Mystic River” and “Poseidon.”