With both sides going into the clash at the Mage Solar Stadion without a win in the Bundesliga this term, the home side were twice thwarted in their attempts to get on the board by the 28-year-old.
Having cancelled out Marc-Oliver Kempf's opener before half-time, Ronny left it until late in stoppage time at the end of the game to ensure a point for Jos Luhukay's side - who had Nico Schulz dismissed late on.
Freiburg opened the scoring after half an hour when Kempf rose highest to head Jonathan Schmid's outswinging corner past Thomas Kraft.
However, the hosts did not lead for long as Ronny equalised with his second goal of the Bundesliga campaign six minutes later.
The Brazilian expertly curled a free-kick over the wall and past Roman Burki to draw Hertha level.
Hertha had conceded nine goals in three Bundesliga matches - more than any other team in the top flight - and that became 11 in four when Freiburg restored their lead.
Vladimir Darida and Karim Guede linked well to forge an opportunity for Felix Klaus who made no mistake and coolly finished from close range 11 minutes from time.
When Schulz was sent off for a professional foul Freiburg seemed on course for a first win of the campaign but, in a dramatic finale, Ronny's driven strike took a deflection in the wall and squirmed out of Burki's reach.