The "Dilwale" actor features in the action-adventure comedy along with John Abraham.
Rohit had previously directed Akshay Kumar-John starrer "Desi Boyz".
"For me honestly it is very emotional. He (Rohit) is my brother and John (Abraham) is my hero in real life. I still remember when 'Desi Boyz' had released, I went to every theatre trying to see what the audience reaction was," Varun told reporters last evening.
"I am proud that it is his madness that has made this film work and that's what you see on screen. That's all him."
"Dishoom" tells the story of two cops, Kabir (Abraham) and Junaid (Varun) on a mission to find an Indian cricketer, who gets kidnapped 36 hours before an India-Pakistan final match.
For his role as a UAE based cop in the film, the 29-year-old "Badlapur" star learnt a little bit of Arabic to get the nuances right.
"The more important preparation was that I am playing a cop based in UAE, Abu Dhabi. I had to learn a little Arabic. There is portion in the film in which we show how cops speak over there is very different from the cops in Mumbai."
While it was emotional for Varun to work in the film, Rohit said on set, the brothers were strictly professional.
"Emotions are only at home. While shooting we were extremely professional in the capacity of an actor and director... Varun is an extremely hardworking hungry actor, who wants to give his best," Rohit said.
"Dishoom", which is scheduled to release on July 29, also stars Jacqueline Fernandez and actor Akshaye Khanna, who makes a comeback after four years.
Rohit is all praise for the "Dil Chahta Hai" star who, he says, has a "great understanding" of script.
"In my limited experience of two films it has been absolute pleasure to direct an actor like Akshaye Khanna. I don't think there is anyone else who has such great understanding of material," he added.
