Her big break came in 1998 when she was cast in the Paul Morrison-directed Solomon a Gaenor, opposite Ioan Gruffudd. Roberts turned up to the audition wearing hiking boots and an old baggy jumper that came down to her knees, having just returned from a two-month trip to South America. With dialogue in Welsh and Yiddish, it won Best Film at the 2000 Verona Film Festival and was nominated for Best Foreign Language Film in the 2000 Oscars.
Her subsequent Welsh-language credits included: Fondue, Rhyw a Deinosors!, Dr Terribles House of Horrible, Border Café, Newes of the Weeke, Y Palmant Aur, Glan Hafren and Pobol y Cwm. She recently played Kirsti O'Shea in S4C's Sopranos-by-the-sea, Y Pris.
In 2009, she starred in the BBC Wales commissioned, Tony Jordan produced hospital drama Crash! as Registrar Mary Finch.
In 2010, she guest starred in the two part Doctor Who Series 5 story, The Hungry Earth/Cold Blood.