Roberts' big break came in 1998, when she appeared in Solomon a Gaenor opposite Ioan Gruffudd. With dialogue in Welsh and Yiddish, the movie won Best Film at the 2000 Verona Film Festival and was nominated for Best Foreign Language Film at the 72nd Academy Awards.

Her subsequent Welsh-language credits include Fondue, Rhyw a Deinosors!, Newes of the Weeke, Y Palmant Aur, Glan Hafren, the long-running soap opera Pobol y Cwm, and S4C's gangster drama Y Pris. Roberts' English-language television credits include the comedy series Dr. Terrible's House of Horrible, the drama Border Café, and several single-episode appearances in prime-time British shows such as The Bill and Casualty.