This plugin is an absolute must for every WordPress site with a registered users system. It offers not only options to customize capabilities to every role, also you can create new roles and assign extra capabilities.
It can make your WordPress private with a single click in plugin options and has a system to restrict content in every post depending of user role.
Also it provides sidebar login form and users list widgets.
It's a great plugin with great features I use in every project when is going to be registered users with different roles.