Late Rosenthal strike sends Freiburg third
Freiburg, enjoying their best ever start with three straight wins from four games, have moved on to nine points with leaders Hoffenheim and Mainz, who have a better goal difference.
The visitors missed an early chance through Papiss Cisse and remained a threat with their swift counter-attacks although substitute goalkeeper Oliver Baumann had to come to the rescue to deny Frankfurt's Patrick Ochs and Caio in the second half.
Freiburg snatched the winner a minute from time, with the hosts complaining Maximilian Nicu was off side when he set up new signing Rosenthal, who slotted home from inside the box.
Hoffenheim visit Kaiserslautern and Mainz play at Werder Bremen on Saturday when champions Bayern Munich, in 11th place with four points from three games, host Cologne.