Hi Laurent!
Yes for both, if you use a Debian or Ubuntu server; previously provy already supported specifying a Python library version through pip, and since version 0.5.0 (released this week) it also supports virtual environments through VirtualenvRole.
For more detailed info on how to use them, I'd suggest you to take a look at the provy.more.debian packages documentation here:
http://heynemann.github.com/provy/#debian - this documentation is pretty extensive and should be easy to understand, but in case you have any further questions, suggestions or comments please don't hesitate and reach us again. :-)