It was a crucial loss of points in their quest for automatic promotion but their second-half performance was nothing like that of a side looking to go up.
They could have had no complaints when Torquay substitute Elliott Benyon forced home the equaliser with just five minutes to go following a long throw-in.
To add to Rotherham's problems they had midfielder Gary Roberts sent off in stoppage time for a second cautionable offence.
Rotherham may consider themselves unfortunate in the first half after striking a post twice within minutes.
Firstly it was Roberts with a rasping drive from outside the penalty area after 15 minutes and shortly afterwards Adam Le Fondre hit the same post with a superb effort.
However, Torquay had their moments too and former Barnsley midfielder Nicky Wroe brought a fine save from Andy Warrington with a shot from distance. The Rotherham goalkeeper also excelled when keeping out a header by Mark Ellis.
Rotherham struck in the 20th minute when midfielder Danny Harrison scrambled the ball home from Nicky Law's centre for his third goal of the season.
However, Rotherham did not improve after the goal and spent much of the second half holding onto their lead and were grateful when Ashley Barnes blazed a sitter over the top from close range.
Rotherham looked set to survive until substitute Benyon punished their poor showing with his late strike.
Rotherham United: Warrington; Lynch, Sharps, Fenton, Gunning (Joseph, 42); Law, Roberts, Harrison, Ellison (Taylor, 71); Pope (Brogan, 83), Le Fondre. Unused substitutes: Mills, Cummins, Marshall, Annerson.
Torquay United: Bevan; Robertson, Ellis, Branston, Camara (Rowe-Turner, 46); Macklin (Benyon, 71), Mansell, Wroe, Thompson (Carayol, 82); Barnes, Zebroski. Unused substitutes:Nicholson, Stevens, O'Kane, Searle.
Referee: N Miller (Co Durham).