Yes, shouldn't be much of a problem.
Just download as many WUs as you want, cut and paste the whole BOINC folder on your pendrive, cut and paste on the PC without connection, and let it crunch.
The only thing that might be odd is that in the "computers on this account" option on the Rosetta site, you'll see two computers with the same name as the one you send the WUs away from. The connection-less PC will adopt the name of the one PC where you download WUs and sneakernet them. But that's a minor thing.