The Germany midfielder - nicknamed 'The Hammer' - unleashed a trademark 25-yard drive into the bottom corner 12 minutes from time to rescue a point for Avram Grant's side after Jason Roberts' early opener.
Without the injured Scott Parker, the Hammers were woefully short of invention and looked to be on their way into the npower Championship after six seasons in the top flight.
The opener arrived after just 12 minutes. Jermaine Jones was allowed to carry the ball from midfield before feeding the overlapping run of Brett Emerton. The Australian was in space after Wayne Bridge had been left upfield and steadied himself to deliver a perfect cross, which Roberts volleyed past Robert Green from five yards out.
Morten Gamst Pedersen then headed a Manuel Da Costa effort off the goalline as the hosts launched a rare attack, but Rovers looked comfortable throughout.
An equaliser looked unlikely until Hitzlsperger struck with time running out. Carlton Cole crafted the chance with good work on the left of the penalty area and he was able to tee up the former Aston Villa midfielder in space in the D. Hitzlsperger took aim and cracked a thunderous drive through a crowd of players and into the far corner.
Source: PA
Source: PA