additional-capabilities.php

// GIVE additional capabilities to 'Manager'
function additional_role_caps( $caps ) {
	$user = wp_get_current_user();
	if ( in_array( 'manager', (array) $user->roles ) ) {
		$caps[ 'edit_theme_options' ] = true;
		
		$caps[ 'list_users' ] = true;
		$caps[ 'create_users' ] = true;
		$caps[ 'delete_users' ] = true;
		$caps[ 'edit_users' ] = true;
		$caps[ 'promote_users' ] = true;
	}
	return $caps;
}
add_filter( 'user_has_cap', 'additional_role_caps' );

new-role.php

// CREATE new role based on Editor
add_action('init', 'cloneUserRole');
function cloneUserRole() {
	global $wp_roles;
	if (!isset($wp_roles))
		$wp_roles = new WP_Roles();
	$auth = $wp_roles->get_role('editor');
	$wp_roles->add_role('manager', 'Manager', $auth->capabilities);
}

remove-custom-role.php

remove_role( 'author' );

remove-role-choice.php

// REMOVE 'Administrator' from the list of roles if the current user is not an admin
function remove_admin( $roles ){
	if( !current_user_can('administrator') ){
		unset( $roles['administrator']);
		unset( $roles['manager']);
	}
	return $roles;
}
add_action('editable_roles','remove_admin');

remove-user-from-list.php

// REMOVE Admin user from user list
add_action('pre_user_query','isa_pre_user_query');
function isa_pre_user_query($user_search) {
	$user = wp_get_current_user();
	if ($user->ID != 1) { // Is not administrator, remove administrator
		global $wpdb;
		$user_search->query_where = str_replace('WHERE 1=1', "WHERE 1=1 AND {$wpdb->users}.ID<>1",$user_search->query_where);
	}
}