I did some testing and can confirm that enabling GuestPass Self-Service will 1) remove all previous guest passes associated with the WLAN, and 2) not allow Guest Pass generation role users from being able to create Guest Passes, for that WLAN.
I found that if I defined a second Guest Access WLAN, not pointed to a service that had GuestPass Self-Service enabled, and expanded the Guest Admin role to include both WLANs, that the admin could create guest passes for the second Guest Access WLAN.
I documented this in KBA-5059, available after the next support site 6 hour KBA update cycle.
https://support.ruckuswireless.com/answers/000005059