Since we went to weekly releases, the name of the release has been stored as the name of the release tarball, but not the release itself. Thus the path itself will contain the data you want, unless whoever installed Rosetta renamed the default path. (In other words, the tarball Rosetta_wk34_2013.tar.gz untars into directory Rosetta_wk34_2013.
This week and next week’s weeklies will have some new features developed from requests at the most recent Rosetta developers meeting, one of which is this sort of tagging. What range of Rosetta builds are you targeting? (3.0-3.5, plus several months of weeklies have been released; 3.6 will retroactively be January 1 release of this year).