an internet connection would make things a lot easier, but if you've got a usb drive to move the files on then it can be done. Its probably not wise running directly from the USB drive though as they have a limited write capacity.

You just need to install boinc to a different folder than it runs in on the internet connected comp, and get it running Rosetta. Get a large queue and set a long run-time so it's got plenty to do. Then Exit BOINC and copy the folder to the same folder on the no-net computer, and start it by running boincmgr.exe.

You just need to exit BOINC and copy it back to the same location on the net pc every time to send/receive.

Just incase, if you need to change the location that Rosetta is running from, it's stored twice in the file BOINC\\slots\\0\\init_data.xml
HTH
Danny