Issue
Every time I create a content type, there are new roles created per content type. Is this a D8 feature or something in Lightning, and can it be turned off?
Resolution
For an existing site, just uninstall lightning_roles. If you want to exclude it entirely from new site builds, use a sub-profile and add lightning_roles to the excluded_dependencies array.
Cause
Auto role creation is a part of the Lightning Roles component. More information can be found in our documentation on Lightning Roles.