The Professor Emeritus of Astronomy at the University of Glasgow was a a consultant to Nasa as it prepared to send a man to the Moon in the 1960s.
However, he was more famous for his lifelong interest in the paranormal. He founded The Scottish Society for Psychical Research in 1987 and wrote many scientific papers and books on the subject.
Yesterday, Professor John Brown, the Astronomer Royal for Scotland who worked with Professor Roy at Glasgow, paid tribute to his former colleague.
"Intellectually, he was one of the last great polymaths; he was interested in so many things," Professor Brown said. "But his subject as an astronomer was the mechanics of orbits and he was the world authority on that. Much of the research was done before computers."
It was Professor Roy's work in this area in the 1960s that led him to becoming convinced man would get to the moon before the end of the decade. In 1964, he placed an £11 bet, at 150-1 against, that the Americans would land on the moon by 1971.
When they did, he collected £1200, which at the time was enough to pay half of the cost of a semi-detached house in Kelvindale.
Professor Roy went on to carry out consultancy work for Nasa into the 1970s, but his interest in the paranormal took up much of his time. His son Ian, 46, said his father had wanted to apply scientific rigour to the subject.
"He was a scientist so his interest in the paranormal was as a scientist," said Ian. "It wasn't a mystical or quasi- religious interest; he was trying to prove scientific concepts. He didn't see boundaries where other people saw them. For him, scientifically, nothing was off-limits."
He published more than 20 books, including one, A Sense of Something Strange, for which Alasdair Gray created the cover. His last book, The Eager Dead, which Professor Roy saw as his most important work, was published in 2008.
The books, and Roy's appearances on TV and radio, did much to popularise interest in psychical research and phenomena. He worked as a consultant on the 1970s BBC Scotland drama The Omega Factor, about a government body that investigates paranormal powers, and later was the inspiration for the Bill Paterson series Sea of Souls.
In his later years, Professor Roy continued to teach at Glasgow University, contributing to evening classes in pyschical research well into his 80s.