"WordPress uses a concept of Roles, designed to give the blog owner the ability to control and assign what users can and cannot do in the blog. A blog owner can manage and allow access to such functions as writing and editing posts, creating Pages, defining links, creating categories, moderating comments, managing plugins, managing themes, and managing other users. The tool that gives the blog owner this control is the ability to assign a Role to a user.
WordPress has five pre-defined Roles: Administrator, Editor, Author, Contributor and Subscriber. Each Role is allowed to perform a set of tasks called Capabilities. There are many Capabilities including publish_posts, moderate_comments, and edit_users. The default Capabilities are pre-assigned to each Role." - WordPress.org
However, by default, WordPress doesn't come with a role editor. Also, most of the time, the default roles and permission just can't meet our project specification/business model. As a result, these plugins will help you configure existing roles and impose a stricter policy to your content and backend access control.
- Adminimize Visually compresses the administratrive meta-boxes so that more admin page content can be initially seen. The plugin that lets you hide 'unnecessary' items from the WordPress administration menu, for alle roles of your install. You can also hide post meta controls on the edit-area to simplify the interface. It is possible to simplify the admin in different for all roles.
It's really comprehensive, you basically can set permission and change access control of everything you see in WordPress backend. It even let you control the write option for post and page!
- Role Manager This Plugin allows you to define and manage multiple subscriber profiles - called Roles and their Capabilities. Also you can create new Roles and Capabilities.If you use this Plugin to manage your Wordpress, Users can belong to only one role and can have individual capabilities assigned to them outside of the context of a role.
Role manager has a really user friendly interface compare to others. It allows you to create roles and capabilities and assign it to users. Of course, you can manage the existing roles and capabilities as well.
- Role Scoper Role Scoper is a comprehensive enrichment for capability enforcement and administration in WordPress. Assign reading, editing or administration roles to users or groups on a page-specific, category-specific or other content-specific basis.
This would be the most powerful and the most confusing role management plugins among all others. The customization level is astonishing. It even allow you to specify the access control to each of the pages that you've already created. If you want to create a really strict and detailed policy, try this plugin.
- User Permission User Permissions is a plugin that takes the simple WordPress permissions models one step further and allows you to assign permissions to specific posts that restrict users or roles from reading or editing it.
This is a small little plugin that does exactly what it said. It allows user to create post/page specific permission right.
- User Role Editor User Role Editor WordPress plugin allows you to change standard WordPress user roles capabilities with easiness of a few mouse clicks. Just turn on check boxes of capabilities you wish to add to the selected role and click “Update” button to save your changes.
A pretty straight forward plugin to customize user role. It's easy to understand compare to Adminimize, roles manager and role scoper but it has limited features.