Roshan made a surprise cameo in Khan's Don 2 - The Chase Continues, and Khan is reportedly keen to return the gesture.
"Hrithik and Shah Rukh have been meeting up to discuss Shah Rukh's cameo in the film," a source close to the two actors told The Times of India.
"With SRK having already done a superhero film, it could be a Krrish and Ra. One reunion in one of the climactic scenes. Since they share a great rapport, it shouldn't be difficult for either one of them."
Details of the Ra.One actor's role in the sequel to Krrish are not yet known.
Roshan and Khan have known each other since the Zindagi Na Milegi Dobara star assisted his father Rakesh Roshan in his film Koyla.
Khan starred alongside Madhuri Dixit in the film.
The actors' wives Suzanne Roshan and Gauri Khan are said to be good friends, and have also recently launched an interiors and furnishings business together.
Khan has also appeared as a guest on talent show Just Dance, on which Roshan is one of the judges.