DO NOT ATTEMPT TO INSTALL ROSETTA IN LION (or Mt. Lion)!
There have been reports of earlier users of FCS2 and FCE 3.5 who did attempt to install Rosetta in Lion some time ago, now experiencing "unexplained" crashes and other symptoms of unstable systems, since applying updates to their Macs (updates of Lion or upgrades to Mt. Lion).
If you have already attempted to install Rosetta into Lion or Mt. Lion, please review this thread on how to IMMEDIATELY remove Rosetta from your operating system:
https://discussions.apple.com/thread/5033680
The SAFEST way to install FCS2 or FCE 3.5 into Lion is to use Pacifist, although there is also a method using Terminal explained by Jeremy Johnstone on his blog:
http://www.jeremyjohnstone.com/blog/2012-03-11-installing-final-cut-pro-studio-2 -0-on-mac-os-x-10-7-lion.html