A frantic start to the game on Tuesday night saw three goals scored in the opening 15 minutes but Luke Freeman's late header ensured a share of the points.
Rotherham took a sixth-minute lead following a swift and clinical move. Jon Taylor controlled a difficult ball out on the left flank and passed it on to Richie Towell, who teed up captain Will Vaulks to smash into the bottom corner from the edge of the box.
The visitors were level on 12 minutes after Ryan Williams failed to clear a cross and Nahki Wells showed his predatory instincts to poke beyond Marek Rodak.
Rotherham hit straight back and were in front again in the 15th minute. Vaulks' chipped free-kick was met strongly by Clark Robertson, who nodded over Joe Lumley for his first Millers goal.
Taylor had Rotherham's best chance to extend their lead after he turned and shot just over the bar from Towell's pass.
The first opportunity of the second half fell to QPR's Pawel Wszolek but he fired off target while off balance.
At the other end, Semi Ajayi latched onto a hopeful ball from Zak Vyner but shot straight at Lumley when unmarked.
QPR dangermen Freeman and Ebere Eze came more into the game in the second half, with the latter going on a menacing run which was eventually blocked by the Millers defence.
Freeman then laid on a huge chance for the visitors to level. He found space against Joe Mattock and whipped in a tremendous ball which Wszolek somehow failed to get a decent connection on.
A good opening then fell to substitute Tomer Hemed but he toe-poked his shot straight at Rotherham goalkeeper Rodak.
Rotherham's own substitute Richard Wood had the next chance but he headed over from Joe Newell's corner.
Ajayi, who had moved into midfield following Wood's introduction, almost put Rotherham further in front but his curling effort from the edge of the box whistled just over the bar.
Another unlikely source threatened to seal the points for Rotherham when Mattock marauded forward from left-back before dragging a shot with his weaker right foot harmlessly at Lumley.
Rodak was called into action for Rotherham when he palmed Freeman's curling strike behind for a corner. From the resulting set-piece, Eze hit a stunning volley which again had to be clawed out acrobatically by Rodak.
Rotherham invited late pressure onto themselves and were made to pay in the first minute of added time as Freeman's diving header beat Rodak.