From: https://eventespresso.com/topic/all-registrations-csv-report-3/

remove_all_csv_button.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

// remove the add registrations csv report button for non-admins
// 

add_action( 'admin_footer', 'my_remove_all_registrations_csv_button' );
function my_remove_all_registrations_csv_button() {
    $screen = get_current_screen();
    if ( $screen->base != 'event-espresso_page_espresso_registrations' ) {
        return;
    } else {
        if ( ! current_user_can( 'ee_read_others_registrations' ) ){
        ?>
            <script>
            jQuery(document).ready(function($) {
              $('#all-registrations-csv-report').remove();
            });
            </script>
        <?php
        }        
    }
}