Ryan brought the curtain down on his 15-year reign hours before Rovers' Sky Bet Championship fixture against South Yorkshire rivals Barnsley on Saturday.
News of his departure began to filter through during the early stages of the goalless draw at Oakwell, where Doncaster supporters sang during the second half ''there's only one John Ryan'' in recognition of what has been achieved during his time with the club.
Reports this week hinted at a fall-out between Ryan and the rest of the board over the protracted takeover of the club by Sequentia Capital.
And the 61-year-old confirmed the disharmony is centred around a meeting this week between Rovers representatives and the Irish-led consortium.
The meeting went ahead without Ryan - much to the annoyance of the man who originally brought Sequentia to the table.
Ryan also questioned the football club's impending takeover of the town's rugby league team, which is set to be officially announced in the coming days.
''Firstly I would like to say it's a very sad day,'' Ryan told Press Association Sport.
''I would like to thank the fans for the reception they gave me, what a send off that was, and for their support over the years, and I hope they continue to support Doncaster Rovers.
''I felt something needed to change as I was feeling increasingly isolated. But when I sold the majority of my share to make it a partnership of three, I knew I could be out-voted.
''I think it is common knowledge that I was very disappointed the Sequentia deal didn't go through. I felt I had one more big push in me - one more promotion - and if they had been allowed to come in with the money then it would have been great.
''The second deal was money up front, which is why the first deal didn't happen despite signing heads of terms.
''But the board seem to think we were better off in League One and I don't share that school of thought, you must keep progressing - going forward.
''And when we spent £100,000 on the rugby club when we needed it on the football side, well, I despair. Honestly.
''The board was lacking ambition and I was cut out of the process - there was a meeting and I wasn't informed. I didn't have any power left as they could out-vote me every time.''
Ryan, who left the directors' box at Oakwell to finish the game in the stands amongst the Doncaster fans, added: ''Basically Sequentia have been told not to speak to me now, which is ridiculous.
''I brought Sequentia to the table and I felt that was taken away from me - and the club. Perhaps other people are trying to put their name to it and take the credit.
''I'm not sure whether talks with Sequentia are still ongoing but if the deal goes through, even without me, I will be delighted because it is the best thing for Doncaster Rovers.
''I sincerely hope the club goes forward and gets success because I am a fan, that's what I will just be from now on - a fan.
''I've been a fan since 1958 and I wanted to end my reign as it began - among the fans.''
Ryan's reign as chairman has coincided with the most successful era in the club's history, including four promotions, a first major cup win in the Johnstone's Paint Trophy and a return to the second tier for the first time in half a century.
Sequentia, supported by a wealthy Belize-based tycoon, was first linked with a takeover of Doncaster in June following the club's return to the Championship.
The consortium pledged to spend upwards of £20million to help propel Rovers to the Premier League and a heads of terms agreement was subsequently signed by both parties.
Ryan supported Sequentia's bid but a boardroom split ensured that the offer was not accepted.
Despite seeing its bid rebuffed, Sequentia remained keen to do a deal.
It has remained largely in the background since, although it did agree a deal last month to purchase a small club shareholding - buying around 1.3 per cent of the club's shares from former chairman Trevor Milton and ex-director Michael Garrity.
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