Jerome's 46th minute strike, however, sealed Birmingham's win which was achieved despite the early sending off of Medhi Nafti.
They were often indebted to the saves of Northern Ireland goalkeeper Maik Taylor for keeping them in the game.
Earlier, Birmingham were somewhat embarrassed by the skill of Doncaster and were badly disjointed at times with the midfield struggling to get to grips with the Yorkshire outfit.
This frustration manifested itself in the 24th minute when Nafti was justifiably sent off for a two-footed tackle on James Coppinger.
Birmingham were sadly off colour with Quincy Owusu-Abeyie producing a dismal performance compounded when the home side were reduced to ten men.
The pace of Lewis Guy and Gareth Taylor posed problems for Birmingham's defence as the home side struggled to stay in the game.
Manager Alex McLeish eventually decided to replace Owusu-Abeyie with Scotland international James McFadden and at half-time veteran Kevin Phillips made way for Marcus Bent.
But not even McLeish could have envisaged the immediate impact that Bent would have on the game as Birmingham took a shock lead 42 seconds into the second half.
A free-kick by Liam Ridgewell was headed on by Bent for the athletic Jerome to volley the ball past Neil Sullivan.
The goal certainly lifted Birmingham and they should have increased their lead in the 48th minute.
Bent cleverly sent Seb Larsson clear but the tenacious Birmingham player shot straight at Sullivan from about 15 yards.
Doncaster still contrived to play some cultured football to demonstrate the progress they have made since their struggles in the Conference a few years ago.
They were always prepared to shoot on sight with skipper Brian Stock producing their best effort with a long-range effort which Maik Taylor confidently handled without too much trouble.
With the exception of their early purple patch at the start of the second half, Birmingham were often forced to play second fiddle as they settled for a survival battle to protect their slender lead.
They continued to live dangerously as highlighted in the 70th minute when Doncaster's shoot on sight policy very nearly gave them an equaliser.
Substitute Darren Byfield forced Maik Taylor to scramble to his left to finger-tip the shot onto the post.
Doncaster came that close to an equaliser as Birmingham were given an early warning that their promotion ambitions are not going to be as easy as some people imagine.