My plugin does NOT create the participant role. That sounds like a BuddyPress role (forum participant).
For public side, the user role makes no difference at all for my plugins, as none of it is role based. Users are either logged in or they are not, and you can set what they can see and do if they are logged in or not in the options for my plugin.
The only role my plugin creates is the Sign-up Sheet Manager role, which is a copy of the WordPress “Author” role with the added capability of “manage_signup_sheets”. That way you can allow an Author type role access to Sign-up Sheets without giving them full admin capabilities.
