The film has been in news due to speculations over who will be cast opposite Ranbir but, Imtiaz says that he is yet to finalise the female lead.
Eros International will co-produce the film with Shri Ashtavinayak Cinevision.
"Eros and Imtiaz Ali have had a fabulous and successful working relationship in the past and we are proud to take our association to the next level with Rockstar in association with Shri Ashtavinayak," Sunil Lulla, Executive Vice Chairman and Managing Director, India-Eros International said.
He said Eros's first film with Ranbir 'Anjana Anjanee' also starring Priyanka Chopra releases this July and the company had an exciting working relationship with him.
Imtiaz said his earlier movies 'Jab We Met' and 'Love Aaj Kal' were both musical romantic entertainers and 'Rockstar' completes the trilogy.