But Dale will still fancy their chances of making the League Two play-off final after a blistering display in the north-east heat.
Despite the importance of the game neither side showed any nerves in a busy opening to the match. Darlington attacked from the first whistle, but a cross from defender Ben Parker was too deep.
Rochdale keeper Tommy Lee had to be at his best in the seventh minute when saving a shot from Scott Wiseman and he then denied Rob Purdie three minutes later.
In between those two efforts, Dale striker Chris Dagnall had seized possession from Alan White and from 20 yards saw his curling shot beat keeper David Stockdale and then crash against the crossbar.
The game settled down after the frantic start and, in the 28th minute, the deadlock was broken when Quakers midfielder Jason Kennedy fired a curling right-foot drive into the top corner of the net from the edge of the area.
There were further chances for both sides in a pulsating opening 45 minutes. Darlington defender White headed a corner from Parker narrowly wide in the 33rd minute and then, two minutes later, Dale captain Gary Jones fired well wide from a good position.
Darlington striker Tommy Wright headed over in the 47th minute as the hosts looked to increase their lead and give themselves a cushion going into the second leg at Spotland.
Dagnall again went close in the 54th minute when he burst into the area but failed to hit the target and then Darlington were unfortunate when Wright hobbled off in the 64th minute.
Six minutes later Rochdale were level when Dagnall's shot took a wicked deflection which left Stockdale wrong-footed.
In the final ten minutes Darlington lost two more players when Parker and White went off with leg injuries.
However, substitutes Neil Wainwright and Miller combined in stoppage time. Miller headed in Wainwright's free-kick from six yards to give Darlington a narrow advantage.