I currently have three user roles on my site, all with different permissions. All I want to do is use this plugin for is to allow members to subscribe to remove adverts. 

I was thinking of creating a forth role called 'No Ads', and using this role to remove them.

My question is, does the plugin simply add users to a new role, or will it remove them out of the roles they were currently in? Also, when they stop subscribing, will it just remove them from the role they were added to.

I hope this makes sense.