The actress looked exquisite in a white dress with ruffles and lace detailing at the front as she joined co-star Cate Blanchett on the red carpet on Wednesday morning (14 October).
Rooney, 30, has already received critical acclaim for her role in Carol, picking up the Best Actress Award at the Cannes Film Festival earlier this year.
Carol is based on the novel The Price of Salt by Patricia Highsmith, which tells the story of a young photographer's relationship with an older, married woman.
Rooney can also be seen playing Tiger Lily in the new Peter Pan movie Pan, co-starring Hugh Jackman. It's in cinemas now.