Updating the WoWRoster from the Armory isn't a 'vbulletin' question but a WoWRoster question, and is done with a Roster addon (all details are in the concerning ArmorySync forum).
Keep it mind, that Blizzard DOES NOT expose an interface or manual about "how to do so", it evens seems to block "massif Armory requests" ones in a while.
It's a "great if it works - and bad luck if it doesn't".
So, a roster updates itself by Guild member intervention. And sometimes, ArmorySync ‘procs’ (

) and helps you updating these last "I can't do that" members.
I can understand why you want to integrate. Your site will look nicer and will be even more acsesible, that's for sure.
But integrating huge project like WoWRoster and a CMS system needs more then installing a plugin and go .... so you need to patch the code heavily.
Meaning, every time you have to apply an update, you have to re-patch again (if things didn't just break).
This means that only you can be the expert of your site, because you have to know everything of your site, because it’s unique.
That’s the price of being beautiful: one way or another, you pay.
Without using money, but much of your time.