She is known for her portrayal as Fiona Gallagher in the television series Shameless.
She has since starred in Poseidon (2006), Dragonball: Evolution (2009), Dare (2009) Beautiful Creatures (2013), Before I Disappear (2014), You're Not You (2014) and Comet (2014).
In 2007, Rossum released her debut album, Inside Out.
She also released a Christmas EP the same year, titled Carol of the Bells.
In 2013, she released a follow up album called Sentimental Journey.
Over the course of five years, she sang onstage with the chorus and had the chance to perform with great singers such as Plácido Domingo and Luciano Pavarotti.