The Reds were rocked on Thursday when the popular German opted to leave Oakwell in favour of linking up with his recently-appointed compatriot Jan Siewert at Huddersfield.
But the Tykes overcame that and Dale netting the opener through Dean Henderson as strike pair Kieffer Moore and Cauley Woodrow found the net.
The victory extended Daniel Stendel's side unbeaten streak to seven League One matches, taking them up to third in the table, only two points off the top two.
The visitors started the better of the two teams, as Stephen Dooley’s lay-off found Callum Camps on the edge of the box but he sliced his shot wide.
In a half of few chances, it was Ryan Delaney who came closest to an opening goal for Rochdale but he volleyed over from close range.
Moore had a goal ruled out for offside shortly after the break, but it was the visitors who took the lead through Henderson in the 49th minute.
Jimmy McNulty took a quick free-kick to beat the offside trap and find Henderson, who coolly slotted home inside the box.
The hosts replied soon after, as Moore equalised five minutes later with a drilled shot into the bottom corner from outside the box.
Barnsley then got the winner in the 75th minute after Jacob Brown beat his man and squared the ball to Woodrow, who made no mistake from six yards.
Barnsley: Davies, Pinnock, Lindsay, McGeehan, Woodrow (Adeboyejo 90), Cavare, Moore (Green 78), Thiam (Dougall 46), Mowatt, Williams, Brown.
Subs: Greatorex, Hedges, Jackson, Pinillos.
Rochdale: Lillis, McLaughlin (Matheson 76), McNulty, Delaney, Ebanks-Landell, Dooley, Andrew (inman 82), Camps (Wilbraham 81), Holden, Hamilton, Henderson.
Subs: Norman, M Williams, Williams, Adshead.
Referee: Alan Young