Software company has sent me Pre-Configure Windows 2012 R2 Std VM and asked me to set it up on our Hyper-V host 

I've done that BUT will I be able to Activate this some how ?

(I've seen some posts about activating OEM with OpenLicense but not the other way around !

Long as its legal I don't have a problem calling Microsoft if necessary for activation!

I don't know how the licensing works & I don't want to look stupid.

 I imagine with Virtulisation this may be regular thing

What is an "ROK version of Windows Server"? 

If the company is sending you a VM they want activated, they should activate it before sending it to you.

For licensing questions, it is best to talk to a trained Microsoft licensing specialist.  You can call Microsoft and talk to them about your unique situation.  Depending upon legal advice from a technical forum is a sure way to end up with non-legally binding advice.

What you are doing is NOT a regular thing because, to my knowledge, Microsoft does not have provisions in their licensing model for shipping VMs between companies.  Hence the need to talk with a trained Microsoft licensing specialist.

ROK - Reseller Option Kit  ie. HP OEM attached to the Physical Server!