Rovers were left having to settle for a point in a match they dominated at Ewood.
Steve Kean's side created the lions share of the chances but were left frustrated against a stubborn Birmingham City side.
Rovers started brightly with Jermaine Jones, Chris Samba and Ryan Nelsen all going close, but it was the visitors who took the lead against the run of play just past the half hour, Lee Bowyer looking suspiciously offside as he headed home Cameron Jerome's centre from inside the six yard box.
Sebastian Larsson then almost doubled Birmingham's lead when he struck the post with a 20 yard free-kick.
Rovers rallied and deservedly levelled on the stroke of half time after Junior Hoilett robbed Liam Ridgewell to race away, round Ben Foster and stroke the ball home.
The second half was a procession of chances in Rovers' favour, Roque Santa Cruz heading against the bar, whilst Benjani, Salgado, Pedersen and Emerton all going close.
Chris Samba had the last chance of the game, but he headed narrowly wide in injury time.
The draw wasn't the result either side were looking for, how important the point proves to be in the shake up remains to be seen.
Fresh from last weekend's well-earned point at the Emirates manager Steve Kean made just the two changes to his starting line-up.
One was enforced as the three-match suspension to Steven Nzonzi meant a return to the starting eleven for David Dunn, whilst fit again Morten Gamst Pedersen was preferred to Brett Emerton who dropped to the bench.
In the Ewood Park sunshine Rovers were bright out of the blocks. Just a minute in Junior Hoilett set out his intentions with a jinking forward run down the right. He found Jermaine Jones advancing into the box, but the American slipped as he prepared to shoot, his subsequent effort lacking accuracy.
Then on five minutes Christopher Samba was inches wide with a glancing header as he connected well at the back post from Morten Gamst Pedersen's free-kick. Another Pedersen set piece found Ryan Nelsen rising high in the area, but headed straight at Ben Foster in the Birmingham goal.
Backed by a noisy crowed Rovers continued to force the pace, Olsson's fine run into the area deserved more, whilst Hoilett was penalised for a handball as he shot through a crowded box.
However there was concern in defence as Chris Samba fell awkwardly when leaping for a challenge, the Rovers captain looking in some pain as he received treatment from physio Dave Fevre. He was helped to the touchline but thankfully returned.
The first half hour had seen the visitors offer very little as an attacking force but it was them who took the lead in contentious circumstances on 32 minutes.
Firstly Jermaine Jones appeared to be fouled by Craig Gardner before the ball was fed onto Cameron Jerome, the striker charged into the six yard box to clip the ball to a suspiciously offside Lee Bowyer who headed into the back of the net. Rovers fans and players alike were furious but the goal stood.
Rovers almost hit back straight away but Roque Santa Cruz couldn't direct Junior Hoilett's cross on target with his glancing header.
Steve Kean was then forced to make a change as a centre half couldn't continue. But it wasn't the aforementioned Chris Samba who made way, it was Ryan Nelsen who limped to the sidelines. Jason Roberts replaced the Kiwi with Phil Jones dropping back to centre half.
Santa Cruz rose well to head Salgado's cross goalwards, but the ball is a couple of yards over Foster's goal, but it was at the other end that the goal was threatened more seriously when Sebastian Larsson very nearly doubled the visitors lead with a 20 yard free-kick. The Birmingham wide man unfortunate to see his effort strike the post and bounce to safety.
As the half entered added time Rovers had two further chances to go in at the break on level terms, a cleared throw saw Michel Salgado's effort blocked, Jason Roberts looped a header goalwards only to see Craig Gardner head off the line.
In the melee from those two incidents, City defender Roger Johnson sustained an injury that would mean further added time, and for once it worked in Rovers' favour.
Barry Ferguson played the ball back to Liam Ridgewell and as he took a touch the quick thinking Junior Hoilett pounced to take the ball off the defender. Hoilett raced away towards goal rounded goalkeeper Ben Foster and neatly rolled the ball into the empty net. His fourth league goal of the season.
The boos still rang out when after almost nine additional minutes the half-time whistle blew, they were directed towards the officials as they made their way down the tunnel.
The second half was slower to get going, not helped by the haphazard officiating of referee Chris Foy. Seemingly innocuous challenges brought out the whistle, whilst as genuinely injured players lay prone play continued.
Sebastian Larsson had the first opportunity after the restart, a free-kick similar to the one he struck so well in the first. This time Paul Robinson was equal to his efforts, diving to push the ball aside.
Rovers would then rattle the woodwork themselves, again it was Hoilett who posed the threat, dancing into the area with a series of twists and turns, he stood the ball up to the back post where Roque Santa Cruz leapt but could only divert the ball against the top of the crossbar.
Foster held well from a fizzing Pedersen free-kick, whilst substitute Benjani, on for Roque Santa Cruz, turned well in the box to collect a pass from David Dunn, but couldn't get his effort on target.
Rovers were then dealt another injury blow as Junior Hoilett was unceremoniously body checked by Barry Ferguson and unable to continue. Brett Emerton came on to replace the Canadian with twenty minutes remaining, Ferguson rightly yellow carded.
Play continued towards the Blackburn End in the final stages, Chris Samba hooked an effort over from a Pedersen throw and Olsson was denied by Foster as he stole into the area. Then after Benjani saw his route to goal thwarted by Curtis Davies. David Dunn's free-kick deflected to Michel Salgado but his shot was diverted wide.
The resulting corner kick would see a trademark inswinger from Pedersen but Ben Foster read the situation well to tip over.
Like the first half, some eight additional minutes were played, but there were to be no last minute heroics this time, Chris Samba heading wide a late chance from a corner.
Neither side would have wanted a draw as the game kicked off, the visitors more thankful than Steve Kean's at the outcome.
ROVERS: Robinson, Salgado, Samba (c), Nelsen (sub Roberts 35 mins), Olsson, Hoilett (sub Emerton 69 mins), J. Jones, P. Jones, Pedersen, Dunn, Santa Cruz (sub Benjani 63 mins).
Subs not used: Bunn (GK), Rochina, Hanley, Diouf.
BIRMINGHAM: Foster, Carr (c), Bowyer, Johnson (sub Davies 46 mins), Ridgewell, Larsson, Gardner, Phillips, Jerome, Ferguson, Parnaby.
Subs not used: Doyle (GK), Murphy, Derbyshire, Fahey, Hleb, Mutch.
Booked: Olsson, J. Jones (Rovers), Ferguson, Larsson, Carr (Birmingham).