As far as I can recall, there is no way to expand all the stacktraces in the GUI (if you don't use something AWTRobot or similar...)
There are two other ways to extract all stacktraces to a log,
either use the Parser API (not supported), or the Parser main class (not supported either)
Both of them are referenced in this blog post (which also deals with extracting stack traces): http://isuru-perera.blogspot.co.uk/2015/05/flame-graphs-with-java-flight-recordings.html
It might be a bit different because it's dealing with Java Flight Recorder, but the first version of Java Flight Recorder is quite similar to JRockit Flight Recorder, so it might be worth a try.