Hrithik, looking dapper in a pair of shades and a monochrome outfit with a few top black buttons open, launched the book on an international platform for the first time.
"I am happy and proud to be here. Not everyone gets a chance to talk about how much a brother loves his sister, on an international platform," Hrithik told reporters here on Saturday.
"The book is about my father's incredible journey. His life will inspire me till the day I die. He has shot in places with extreme climate and has experienced tragedies," added the actor, who has penned the foreword of the book.
Rakesh Roshan, who has acted in multiple films like "Khatta Meetha" and "Khoobsurat", is known for directing films like "Khoon Bhari Maang", "Karan Arjun", Kaho Naaa Pyaar Hai" and the "Krrish" franchise.
Calling his father someone who is not "expressive", he said that his sister did the job of expressing how much she loves him.
"She decided to do this magnificent thing. She decided to write this book. She had to make a lot of effort, go to places and do research," said the "Bang Bang!" star.
Sunaina wasn't at the launch, but he made a video call to make her a part of it.
"I am getting bored at IIFA," Hrithik, who on Friday had regaled his fans with impromptu jigs at a mall here, joked to his sister.
For the book, Sunaina took a leaf out of a gamut of photographs from Rakesh Roshan's childhood to teenage days as well as his days as a young handsome actor, when he turned a husband, father, director and on his journey till now, and touched base with his extended family and friends secretly to get the project going.
There are about 30 people, including names like Shatrughan Sinha, Jeetendra and Rishi Kapoor, to whom Sunaina spoke to for getting the most candid information out about her father.