@galaxxyafonso, welcome to the Rockstor forums.
The VM feature is not embedded in Rockstor (yet, at least). However, there has been at least one documented how-to on how you can get that to work with a little tinkering:
To install Rockstor you can look at the documentation, which should give you a straightforward of installing it. Note: Rockstor only considers the btrfs as file storage system (unlike unRAID which recommends to use btrfs only for its cache-pools if I remember correctly), so any previously used drives with other fs on it, need to be prepared.
If you do end up liking and staying with Rockstor, still consider to pay for a license at some point to support the very small development team’s efforts.
Good luck!