That's a functionality that would need to be implemented within the app. That means Google.
Frankly, this is a management issue. If management cared, they could discipline the owner of the added Google accounts, since you can tell who it is. If management doesn't care, and if Google doesn't add the feature to the app, you're fighting a losing battle.
Now, I'd never suggest using another user's YouTube account and playing a bunch of really oddball stuff that would screw up their Google search results. Of course, using their own accounts keeps yours from being impacted, so there's that.
Or, if you have enough pull in the IT department, you could lock down that MAC address during certain times of the day.
Roku Community Streaming Expert
Note: I am not a Roku employee.
If this post solves your problem please help others find this answer and click "Accept as Solution."