Two goals from Adrian Ramos put the hosts in the ascendancy, the first a 17th-minute penalty to cancel out Nils Petersen's opener and the second giving Hertha the lead.
Aaron Hunt got Bremen back on level terms before the interval, but Ronny bagged the winner three minutes after the restart to lift Hertha above Schalke and condemn Bremen to their fourth defeat in five games.
Petersen may have made a hash of Hunt's first cross, but, when he received the ball from his strike partner a second time in the 15th minute, he made amends with a powerful shot past Thomas Kraft from outside the penalty area.
Bremen's celebrations had not even subsided, though, when Theodor Gebre Selassie fouled Per Skjelbred as he cut across him in the penalty area, and Ramos tucked the resulting spot-kick into the bottom-right corner.
Ramos put Berlin in front with his second of the game, playing his shot across the face of Raphael Wolf, whose dive lacked any conviction.
Bremen responded well, however, and Hunt combined well with Petersen once again, this time the roles reversed with the latter's cross setting up the former to level after just over half an hour.
The second half started with similar promise, and Ronny gave Hertha the lead for the second time on the night just three minutes in when Peter Pekarik's effort was saved by Wolf, but only to the feet of Ronny, who side-footed into an empty goal from close range.
The first lull in the game arrived with Bremen unable to impose themselves again.
They went close to levelling late on when Hunt's free-kick was pushed onto the post by Kraft and Levan Kobiashvili covered to clear ahead of the onrushing Eljero Elia and save the points for Hertha.