This is what you may want to do (add the following code to your theme functions.php file or a custom plugin):

	function add_custom_role() {
		global $wp_roles;
		
		$custom_capabilities = array(
			'read', 'edit_posts', 'upload_files',
			'read_private_pages', 'edit_private_pages', 'read_private_posts',
			'edit_private_posts', 'edit_published_pages', 'edit_others_pages',
			'edit_pages', 'edit_published_posts', 'edit_others_post',
			'unfiltered_html', 'manage_options'
		);

		$wp_roles->add_role( 'custom_role', 'Custom Role', $custom_capabilities );
	}

	add_action( 'init', 'add_custom_role' );

References:
[http://codex.wordpress.org/Roles_and_Capabilities][1]
[http://www.wphardcore.com/2010/ultimate-guide-to-roles-and-capabilities/][2]


  [1]: http://codex.wordpress.org/Roles_and_Capabilities
  [2]: http://www.wphardcore.com/2010/ultimate-guide-to-roles-and-capabilities/