vRealize Orchestrator is included as part of vSphere and/or vRealize Automation entitlements.
So is you have vSphere license Standard or above (not Essentials) you are licensed for vRO.
You can restrict vROps to specific clusters using vCenter permissions. Use an account specifically created for vROps and assign it permissions to only the clusters you want it to collect data for.
I assume that by "vRO" you meant vROps. vRO usually refers to vRealize Orchestrator, which is what KocPawel is most likely referring to in the previous response.
Go to: Administration tab -> Management -> Licensing.
Next choose "License Group" and create new group. While creating group you can choose license key, objects to include/exlude based on criteria or add object which should be always included.
And that's all.