Roy, who served as a federal minister, chose to stay in Pakistan after Bangladesh was created from the erstwhile East Pakistan in 1971.
He went on to serve as an ambassador and became head of the All Pakistan Buddhist Association.
He also served as Minority Affairs Minister in the caretaker government before the 2008 general election.
Foreign Minister Hina Rabbani Khar, Minister of State for Foreign Affairs Nawabzada Malik Amad Khan, Foreign Secretary Jalil Abbas Jilani and officials of the Foreign Office expressed their condolences at the death of Roy.
"In his passing away, Pakistan has lost a distinguished diplomat who served the country with exemplary commitment and distinction," said a statement issued by the Foreign Office.