She currently stars in the lead role of Chanel Oberlin on the Fox television series Scream Queens, as well as playing main roles in American Horror Story: Coven and Freak Show. Through her father's marriage, she is the stepdaughter of Eliza Roberts.Through her mother's marriage, she is the stepdaughter of musician Kelly Nickels. Her paternal grandmother was acting coach Betty Lou Bredemus (1934–2015), and her aunts are actresses Julia Roberts and Lisa Roberts Gillan.Roberts said in an interview that her role as Banks tempted her to write an album of songs using her character as an alter ego.
Roberts described her character as "pretty much your typical spoiled-brat Malibu socialite who gets shipped off to British boarding school." Roberts also appeared in the independent film Lymelife with Alec Baldwin, which was premiered at the 2008 Toronto International Film Festival.
In 2010, Roberts co-starred as Grace in the film Valentine's Day in which her aunt, Julia Roberts also appeared, although they were never together on-screen.
After making her film debut as Kristina Jung in Blow (2001), Roberts gained recognition for her lead role as Addie Singer on the Nickelodeon television series Unfabulous (2004–07).
She released her debut studio album, Unfabulous and More (2005), which also served as the series' soundtrack.
She next appeared in season three of the FX horror anthology series American Horror Story, called American Horror Story: Coven, from late 2013 through January 2014.
Roberts portrayed a self-involved party girl named Madison Montgomery, who also happens to be a telekinetic witch.
She also appeared that year in Twelve and It's Kind of a Funny Story.
In 2013, Roberts co-starred with John Cusack and Evan Peters in Adult World.
Roberts then appeared in a series of film roles, including Nancy Drew (2007), Wild Child (2008), Hotel for Dogs (2009), Valentine's Day (2010), It's Kind of a Funny Story (2010), and The Art of Getting By (2011).
Looking for more mature roles, Roberts went on to obtain both supporting and lead roles in Lymelife (2009), 220.127.116.11 (2010), Scream 4 (2011), Adult World (2013), We're the Millers (2013), and Palo Alto (2013).
The film was released in May 2014 to generally positive reviews, with particular praise for Roberts' performance.