Filter Members Directory By User Role.

yzc_filter_members_directory_by_role.php

<?php
/**
 * Filter Members Directory By User Role.
 */
function yzc_filter_members_directory_by_role( $args ) {

    // do not exclude in admin.
    if ( ! bp_is_members_directory() ) {
        return $args;
    }
 
    $included = isset( $args['include'] ) ? $args['include'] : array();
 
    if ( ! is_array( $included ) ) {
        $included = explode( ',', $included );
    }
 
    $user_ids = get_users( array( 'role' => 'administrator', 'fields' => 'ID' ) );
 
    $included = array_merge( $included, $user_ids );
 
    $args['include'] = $included;
 
    return $args;
}

add_filter( 'bp_after_has_members_parse_args', 'yzc_filter_members_directory_by_role' );