Hi Gary McDonald,
Thank you for using our services.
You will get this error if you are setting up a new project using the built in SQL Express database that comes with a creation of a new project, because there are no roles that exist in the role provider during project initialization. If you use your database you should not get this error. As described in previous posts to this thread the project manager is editing the web.config of your site during CMS startup and this gets resolved.
the Telerik team