The home side went behind to a first half Craig Rocastle goal but replied with strikes from Ian Sharps, Will Hoskins and Ritchie Partridge at Millmoor.
On 18 minutes Oldham saw a glorious chance to open the scoring go begging. Pablo Mills hoisted a high clearance into the area and Rocastle headed down but Lewis Grabban stabbed a tame shot that was easily held by Neil Cutler.
Four minutes later the home side came close to grabbing the advantage but Facey's volley from six yards out was cleared off the line by Will Haining.
Oldham, though, showed their experience against the Yorkshire outfit and carved out more opportunities before half time.
Rocastle found space to create an opening and picked out Grabban but his shot in the 23rd minute was deflected wide.
Former Sheffield Wednesday midfielder Rocastle, who had an impressive
display, then linked up with Richie Wellens but saw his shot saved by Cutler at full stretch.
Then four minutes before half time Oldham took the lead after a bizarre build up. Andy Liddell's miscued clearance dropped kindly to Neil Wood, who found Paul Edwards wide on the left, and his cross into the area was met by Rocastle with a firm left-foot shot which beat the diving Cutler.
A mix up between Cutler and David Worrell let in Wellens a minute into the second half but Cutler made amends with a point-blank block.
A minute later Partridge produced a rising shot that substitute keeper Terry Smith topped over the top. But in the 48th minute Rotherham were level after a short corner. Delroy Facey headed down the resulting corner and Ian Sharps hit a rasping shot past Smith.
Six minutes later Rotherham went ahead after Mills lifted a long ball that had Hoskins racing in behind the defence. The young front man kept his cool and clipped a low shot wide of Smith.
And two minutes from the end a free kick from Cutler was headed on by Facey and Partridge raced in to head the ball over the advancing keeper.