For Rose2000 J, your autoexec.bat should have SET CLASSPATH=[drive]:\jdk[v#]\jre\lib\rt.jar. In my autoexec.bat I have it set as D:\jdk1.3\jre\lib\rt.jar.
You can verify if this path exists in Rose via:
Tools>Java>Project Specification>Class Path>Environment Settings
If not, edit your autoexec.bat and most importantly, reboot your computer.
Once you verify your rt.jar exists in Env.. Settings, go to
Tools>Java>Project Specification>Class Path>Directories and add your "C:\Rational" path.
You are ready to reverse engineer any java file under C:\Rational. Go to Tools>Java>Java Reverse Engineer Java and you should see your rt.jar and C:\Rational folder. You know what to do

Note: I had the correct settings before, and it still did not work. Only when I updated my rt.jar from v1.2.2 to v1.3 did the whole thing work. Took me couple of days, wheew.
For a general idea on Rose RE settings look at:
http://cafe.rational.com/HyperNews/get/hn/rosecafe/1977/1.html?nogifs Good Luck
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~James Baud Talk, does not cook rice. - Chinese Proverb