Lukas Jutkiewicz took full advantage of the Millers’ shortcomings in defence when he capitalised upon two bad mistakes by goalkeeper Marek Rodak.
The striker’s best goal was his third in the 68th, which resulted from a well worked free-kick organised in training.
Instead of firing at goal, Jota slipped a short pass to Jacques Maghoma who slid the ball square into the path of Jutkiewicz, who scored with a low raking drive past Rodak.
The Millers produced a strong finish and were rewarded with a 77th minute goal from Jon Taylor, Rotherham’s first goal in five away games.
Millers manager Paul Warne had mixed feelings about the inability to produce three away points. He said: “Their third goal killed us off. We kept going and the way we play we are a difficult team to play against, but we were not our best on this occasion.
“I just think in the first half hour we moved the ball too slowly and tried to be too precise.
“There were a lot of opportunities in the box, but we didn’t capitalise on these chances. It isn’t lack of ability because the lads can score. A few of the lads had an off day.
“Obviously it is massively important to pick up some away points. The lads have been excellent at home and if we had been excellent against Birmingham we would have collected some points for the bus trip home.
“Our away record is not a mental hurdle for me. I felt quite comfortable after 15 minutes. Even after the first goal I believed that we could get back into the game. Collectively I think the game was one too much for us and there were not enough of my players at their best.”
Birmingham City: Camp, Colin, Morrison (Roberts 74), Dean, Pedersen, Jota, Kieftenbeld, Gary Gardner, Maghoma (Mahoney 73), Jutkiewicz, Adams (Lubula 90). Unused substitutes: Solomon-Otabor, Trueman, Harding, Lakin.
Rotherham United: Rodak, Jones, Ajayi, Vaulks, Mattock, Taylor, Palmer (Vyner 88), Manning (Wiles 63), Newell (Vassell 55), Williams, Smith. Unused substitutes: Forde, Price, Manny Onariase, Lewthwaite.
Referee: K Stroud (Hampshire).