Roger was the head of one of the UK's biggest cucumber growers Humber Salads, a big name in Yorkshire grower circles, and a huge driving force behind Stockbridge Technology Centre.
He was also a force behind the 2001 takeover of tomato giant Van Heyningen Bros, which saw the newly-named Humber VHB selling 20 million cartons of salads and herbs a year.
The graduate of biological sciences was also co-owner of family East Yorkshire protected crop grower RM Sayer.
Stockbridge Technology Centre chief executive Graham Ward told Horticulture Week: "I knew Roger for many years and we have lost a champion. He was always helpful and listened carefully.
"In all the years I knew him he never got cross despite building a vast business empire and at times dealing with very frustrating political situations. He was a superb, very effective negotiator.
"But Roger was also a quite family man who with his wife liked to take pioneering holidays. He had time for everybody and was a gentlemanly gentlemen. I have lost a great friend."
Ward said Roger was a member of the original 'rescue' group that negotiated with the then Ministry of Agriculture, Fisheries and Food to ensure it sold Stockbridge House as a going concern.
"Roger worked closely with Michael Holmes to raise the finance from our industry colleagues, which gave us the momentum to get a reversal of the original closure sale.
"When the ministry put the property up for sale Roger led the purchase price negotiations and the discussions with our bank."
Roger Sayer served on boards at STC Research Foundation and STC until last year. He also served on the first Board for Horticulture, drawing up new governance for horticulture within the NFU.
"We also worked together on the Producer Organisations, which have benefited many growers over the years. Roger never appeared to be stressed or phased. He was calm and constructive.
"STC would not be here without his efforts, but Roger was a major contributor to horticulture at a number of levels."
RM Sayer general manager Nigel Bartle said: "At 64, he appeared fit and well and this has come as an incredible shock to family, friends and colleagues.
"In addition to the Humber Growers business Roger played a prominent part in British horticulture, being a founder director of Stockbridge and former chair of the NFU board for Horticulture."
A service will take place at St Helen's Church at Welton in East Yorkshire followed by a private crematorium service for immediate family only.
Well-wishers are invited to attend an event after the cremation. Those wishing to attend have been asked to inform Daphne Sansam via email at firstname.lastname@example.org.