If you're interested in programming with the vAPI and bypassing the powershell host here's some really good information. I've taken from that and have a work around now as well.
Assigning vCenter tags using vRealize Orchestrator – The vGoodie-bag
And yet another possibility if you want to avoid having to muck around with vRO entirely is to use the SovLabs VM Tagging module which is driven entirely through vRA.
Retrieving data ...