Warnock's men put in a battling display against the play-off chasing Birmingham but could not create any clear-cut chances and are now five points from safety after MK Dons surprisingly won at Derby.
Rotherham finished with nine men as Richard Wood and Joe Mattock saw red.
Birmingham also had chances with Paul Robinson heading wide and Lee Camp producing a brave stop to deny Jacques Maghoma.
Key moment
Camp was Rotherham's hero as the goalkeeper raced off his line to deny Maghoma with 15 minutes remaining.
Man of the match
Lee Camp - Made two vital saves to ensure he kept a clean sheet.
The
Line-ups
Rotherham
(4-4-2): Camp, Richardson, Broadfoot, Wood, Mattock, Burke,
Smallwood, Green, Newell, Derbyshire (Clarke-Harris 64), Ward
Birmingham:
(4-2-3-1): Kuszczak, Shotton, Morrison, Robinson, Grounds, Gleeson,
Kieftenbeld; Buckley, Toral, Maghoma, Donaldson
Referee:
Richard Clark
Attendance:
11,018 (2,614)
