XMPP-Module: Adding users to Roster?

Hope its ok if i reference my Answerhub-Question here. But after reading the Documentation of the XMPP module, i know how to get Users from the Roster. But not how to add them. Can i simply do normal XMPP-Queries using XMPPMessage to get this done? Goes the Query into the Body? Is toJID simply left empty? Just a bit lost where to put the parameters(if its possible at all).