The Hollywood star, 31, hit the red carpet with her mum Katia Langenheim, 51, and girlfriend Jessica Origliasso, 32.
Rose has previously opened up about her close relationship with her mum, an artist from Melbourne.
"My first female relationship was with Chiara when I was 17. My mum totally got it that I was gay - she knew before I came out at 12," she told Sunday Life.
"My mum has always been supportive of me and we have a close relationship. You definitely need someone to lean on and she has been great during some tough moments in my childhood and teenage years."
Rose is a new addition to the Pitch Perfect film franchise and plays Chastity, a singer from an opposing girl group.
Also on the red carpet were Rose's co-stars and Rebel Wilson (Fat Amy), Brittany Snow (Chloe) and Anna Camp (Aubrey).
Pitch Perfect 3 hits Australian cinemas on January 1 2018.