Ajay Devgan and Akshay Kumar was offered the role of Robert D'costa but both of them turned down...

Initially the role was offered to Chitrangada Singh. However, the actress was not keen to play the role.
After Chitrangada, the makers approached the 'Murder 2' actress Jacqueline Fernandez for the most coveted role.
Even the actress refused it as it didn't want to do intimate kissing scene with Hrithik and wear bikini in the film.
Nargis loved the script
Buzz has it that Rakesh and Hrithik who had watched the few trailers of 'Rockstar' decided to rope in the actress for the film. Recently the makers even sat for discussion with the actress.
A source has conveyed that Nargis has no issues doing a kissing scene and has given the nod to be part of the project.
“Nargis really loved the script. The modalities are being worked out. It looks like Rakesh Roshan has finally found his heroine.This is a bold role. And Nargis does not have any qualms about wearing a bikini or being intimate with Hrithik on-screen. Her physicality suits the character perfectly. This is exactly what Fernandez was supposed,” stated the source.
Kareena wants to work with Hrithik
Seperately, it is being reported that Kareena Kapoor, who has worked with all leading Khans of Bollywood, has recently confessed that she would love to share screen with Hrithik.
“I would love to work with Duggu, but the real thing is that we haven’t been offered anything substantial together yet. If and when anything that we like comes up, I would love to work with him,” said Kareena.
The actress had earlier refused to do an item number in Hrithik’s 'Agneepath.'