Ryan announced the decision following two days of speculation after the Yorkshire Post revealed that his future was in doubt due to concerns about the future direction of the club on Thursday morning.
Tensions have been fraught among Ryan and Terry Bramall, another of the club’s majority shareholders along with Dick Watson, since a proposed takeover of Rovers by Irish consortium Sequentia Capital was rejected - much to Ryan’s frustration.
Matters again came to a head this week following a meeting between Sequentia and representatives of Rovers main shareholders, a meeting Ryan wasn’t privy to.
Ryan, who took over as chairman 15 years ago, sent a letter to Rovers chief executive Gareth Baldwin informing him of his decision, with the news breaking just before the kick-off.
A solemn-looking Ryan watched the second half with Rovers’ visiting contingent after spending the first-half just in front of the press box - with fans quick to voice their support.
The drama wasn’t restricted to matters off the pitch at Oakwell, with the hosts - seeking to extend their unbeaten run to four games and leapfrog Rovers in the table - spurning the gift of a 19th-minute penalty.
It followed an untidy challenge from Bongani Khumalo on Marcus Pedersen, with Premier League referee Kevin Friend having no option but to point to the spot.
But seven-goal top-scorer Chris O’Grady saw his well-struck effort saved, diving to his right, by Ross Turnbull, who spent a loan spell at Oakwell earlier in his career.
Rovers, without defensive lynchpin and skipper Rob Jones, produced a game display against the Reds, showing plenty of heart and organisation, despite one or two hairy moments.
Seven minutes before Barnsley’s penalty award, the Reds spurned another golden opportunity when big defender Jean-Yves Mvoto, who was poised to join Doncaster in the summer before their Oakwell rivals gazumped them, somehow put a point-blank header off target following Tom Kennedy’s swinging corner.
Following the penalty, Turnbull had to be alert to hold onto a David Perkins effort, while also saving an effort from Paddy McCourt after a trademark run from the ex-Celtic man.
Penalty villain Khumalo headed a half-chance over for Rovers, for whom teenager Luke McCullough had a sound game, deputising for Rob Jones.
The action in the second period was well contested, but both sides struggled for clear-cut chances in the rain, with McCourt seeing an effort turned away by Turnbull, who also held a stinging shot from O’Grady.
Appeals for a penalty were rebuffed after McCourt went down in the box, with Rovers possessing only sporadic moments of attacking threat, with Richie Wellens, Paul Keegan and Dean Furman policing the central midfield.
M’Voto steered an effort wide in the final ten minutes as the hosts sought a breakthrough, while at the other end, Wellens steered an effort wide with Rovers’ best chance of the game.
The game ended with O’Grady heading off target following McCourt’s cross with the Reds forced to settle for a point as Rovers ended their three-match losing sequence with a battling point.
That said, Barnsley almost snatched in at the death with sub Tomasz Cywka heading wide following Kennedy’s free-kick.
Barnsley: Butland; Wiseman, M’Voto, Cranie; Kennedy, McCourt, Fox (Dawson 65), Perkins, O’Brien (Cywka 85), Pedersen (Scotland 75), O’Grady. Unused substitutes: Hassell, Nyatanga, Dagnall, Etuhu.
Doncaster Rovers: Turnbulll; Quinn, McCullough, Khumalo, Wabara; Robinson (Cotterill 63), Wellens, Furman, Keegan, Duffy (Coppinger 80); Brown. Unused substitutes: Maxted, Paynter, Wakefield, Fernandez, Peterson.
Referee: K Friend (Leicestershire).
Attendance: 11,843 (1,925 Rovers).