He said it was a significant day for him and thanked the party. He, however, clarified that he will continue with his acting career.
Roy, 49, made his Bollywood debut at the age of 22 in the 1990 blockbuster 'Aashiqui'. He acted in movies like 'Junoon' and 'Phir Teri Kahani Yaad Aayee'.
He also won the first season of the popular TV reality show 'Bigg Boss'.
The actor said he wants to contribute towards India's development and is ready to take up any task entrusted to him by the party.
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Asked to comment on a row surrounding Sanjay Leela Bhansali-directed movie 'Padmavati', he said as audience and as artist he believes in freedom of expression, but, he added, he believes in respecting feelings and history of the country he belongs to.
"I do not support violence and threat but respecting the history is equally important. I believe a fine solution will come up. He (Bansali) is a sensible filmmaker and the BJP is looking at the broader picture that there should be peace and calm.
The lavishly mounted period film, which centres around the Rajput queen Padmavati, is scheduled to be released on December 1.
Various Rajput groups have been protesting across the country against the film, alleging it "distorts" history and "hurts" sentiments of people.