Stimson had been based in Japan for three years as director of operations, Asia, where he set up the company's Japanese office and rose garden at Hanasaki Farm in Osaka.
In April, he took a year's sabbatical to sail 16,000 miles from Osaka to Southampton in his 38ft yacht. The US Coast Guard and Navy called off the search after 50 hours.
Stimson joined the company in 2004 as a UK sales representative and by 2007 was responsible for wholesale sales and business development in more than 35 countries, including Japan, Russia, Canada and Europe.
David Austin Roses managing director David JC Austin said: "He will be sadly missed."