Hey Brad, I have this same need and issue. Here is how Telerik responded to my support ticket.
on Apr 20, 2012
I apologize for the inconvenience this delayed response might have
caused, and for the initial misleading. Actually the SqlRoleProvider is
not supported in the Sitefinity 5.0 version, due to compatibility issues
newly introduced Claims authentication. Please accept our apologies for
this, and please keep in touch as we will announce if the support for
the provider is resumed.
the Telerik team