can you scan a device that is on a VPN

2 Spice ups

All you need to do is ensure that the VPN subnet (if not a bridged VPN) is routable from your network and that firewall rules allow the scan traffic through. You can specify a scan range just like you would normally for you main network. If you are looking to scan large swaths of machine in a remote VPN (i.e. site-to-site) a remote collector is probably a much better choice. Also if you are doing remote mobile like laptops a remote collector isn’t a bad idea either, thankfully though it is my understanding that Spiceworks is developing an agent which would be much more useful for scenarios like mobile laptops.

VPNs are transparent to devices on the network. So SpiceWorks (or any other networked service) will not even know that the VPN is there.