Dia, who has acted with Sanjay in films like "Parineeta" and "Lage Raho Munna Bhai", had earlier this month said that she has joined the cast of the biopic, being helmed by Rajkumar Hirani.
Now, the film's co-producer Vidhu Vinod Chopra has revealed her role.
"Dia Mirza is doing the role of Manyata," Chopra told IANS at the ongoing Jaipur Literature Festival, 2017.
"It is a biopic and it is more than a biopic too because we expect people to learn something from it," he added.
Chopra also said that among other things, the biopic will also explore Sanjay's relationship with his late star father Sunil Dutt. Veteran actor Paresh Rawal is playing the role of Sunil Dutt, while Sanjay's part is being brought alive by Ranbir Kapoor.
The filmmaker, who has worked with Sanjay in films like "Munna Bhai M.B.B.S.", "Eklavya: The Royal Guard" and "Mission Kashmir", revealed that after Sanjay's release from Yerwada Central Jail last year, the actor used to tell him and Hirani about his life. They thought it could make a good film.
They are looking for a December release.
"I don't make pictures depending on the release date. I prefer to make one picture in four years than four pictures in one year," said Chopra, who is also set to direct a film on Kashmiri Pandits.
"The shooting will begin from September," said the director, who had helmed the film "Mission Kashmir" in 2000.
Will Kashmiri Pandit Anupam Kher star in it?
"It depends on the role for him," said the filmmaker, who is here for the launch of his daughter Zuni Chopra's novel "The House That Spoke". The book by the 15-year-old, also on Kashmir, will be unveiled on Sunday.
Asked about "Raees" and "Kaabil" clashing at the box office on January 25, he said: "Both (Shah Rukh Khan and Hrithik Roshan) are my friends and I hope that both the films do well."
