One of the heroes of Roma's midweek UEFA Champions League comeback against Barcelona, Dzeko was instead frustrated on this occasion as the Giallorossi failed to capitalise on Stefan Radu's 80th-minute sending off.
Romania defender Radu was dismissed for a second yellow, seemingly opening the door to Roma to secure a win that would have taken it ahead of its third-placed city rival.
But it was instead made to be content with a result that moves them a point clear of fifth-placed Inter Milan, which drew 0-0 at Atalanta on Sunday, in the race for UEFA Champions League qualification.
Lazio was not without its own opportunities, Marco Parolo blasting an early attempt high and wide, while Adam Marusic was denied by a vital Stephan El Shaarawy block prior to Dzeko's chance.
The Biancocelesti, though, will doubtless be the happier of the two having inched closer to a top-four berth with six games remaining, in the process holding Roma to back-to-back Serie A blanks for the first time since March 2015.