Roles are a great way to give access to assets in a controlled environment. This means, people only see what you want them to see.
The owner is the highest level user. They can see all Libraries and manage the billing and team members.
An Admin can manage everything except for the billing info. They can see all Libraries and add and remove team members.
A Collaborator only has access to the Libraries that an Admin or Owner has granted them access to. They are able to view Assets in that Library as well as upload new one and edit existing ones.
A Viewer can only browse the Libraries that an Admin of Owner has granted them access to. They cannot comment or upload.