How can a plugin developer expose custom roles?

I want to manage a custom role for another plugin. Do you have documentation that the developer can use to expose that role for use by Members? (Allowing access to the specific plugin to user with specific role. | WordPress.org) I know you can’t go figure this out for every possible plugin, but I also know that some plugins do make their custom roles available in your plugin. Do you have any guidance on how a developer can do this that I can pass along to the developer of the one I am trying to get access to?