Five second-half goals from Mason Holgate, Connor Hourihane, Sam Winnal and a double from Josh Scowen earned the hosts all three points at Oakwell, which saw Dale finish the 2014/15 League One season in eighth spot.
It means the Spotland side surpassed their previous record of finishing ninth in the third tier in the 2010/11 campaign, a feat set by manager Keith Hill during his first managerial spell at the club.
The first meaningful chance came on the 10-minute mark when George Maris found Manchester United loanee Ben Pearson darting inside in the area, who volleyed narrowly over the bar.
Tykes striker Sam Winnall had his head in head in his hands moments later when Maris played him through on goal with only Josh Lillis to beat, but the Tykes frontman couldn’t get a touch on the long ball.
Rochdale nearly capitalised on a defensive mishap from Lewin Nytatanga on 14 minutes, as the Barnsley skipper slipped and lost possession with a chasing Ian Henderson in his midst, but goalkeeper Adam Davies remained alert to deal with the loose ball.
Reuben Noble-Lazarus fired a freekick from the edge of the D which deflected out for a corner on 17 minutes, while James Bree fired over from range shortly after.
Barnsley’s George Smith came close to catching Josh Lillis off guard with his 25-yard strike, before young-gun Joel Logan worked himself into a threatening position in the Barnsley box before being dispossessed on 35 minutes.
Goalkeeper Lillis was on-hand to deny Luke Berry’s close range header on 40 minutes, while hot-shot Henderson tested Davies at the other end shortly before the break.
Dale came close agonisingly to opening the scoring early in the second half when Peter Vincenti’s header was blocked on the line by Davies.
But as the Spotland side were turning up the pressure, they were reduced to ten men on 50 minutes when Joe Rafferty was shown a second yellow for his challenge on Scowen.
The Tykes continued to test Lillis in between the sticks, but the Dale stopper remained alert to deny Maris and Conor Hourihane in quick succession.
Despite being a man down, Dale remained dangerous in attack with their fluid attacking play. They enjoyed another great opportunity when Noble-Lazarus’ 60th minute strike was turned away, while top goalscorer Henderson was denied on the follow-up.
Jamie Allen showed great determination to chase down a long ball before forcing Davies to act on 64 minutes.
Lee Johnson’s side took the lead when Scowen headed home Hourihane’s corner on 67 minutes, before the Tykes midfielder doubled his tally nine minutes later.
The Oakwell side had the ball in the back of the net on 78 minutes, but Winnal’s effort was ruled out for offside.
But substitute George Williams converted Hourihane’s corner on 83 minutes, who sealed a hat-trick of assists.
The Tykes recorded an additional two in injury time when Rhys Oates broke through and played a selfless pass to Hourihane, who tapped in for an easy finish, while Sam Winnall made it five soon after.
ROCHDALE: Lillis, Rafferty, Eastham, Lancashire, Vincenti, Noble-Lazarus (Camps ’68), Tanser, Logan (Allen ’50), Cannon (Bennett ’45), Kennedy, Henderson NOT USED: Musangu, Andrew, Rose, Bunney