This will hide the Export All buttons from the users with the Event Manager role. Event Espresso 3 + Roles and Permissions add-on required.

functions.php

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

add_action('admin_head', 'my_custom_hide_buttons_for_event_managers');

function my_custom_hide_buttons_for_event_managers() {
    global $pagenow;
    if( $pagenow == 'admin.php' && ! current_user_can( 'espresso_group_admin' ) ) {
        echo '<style>
            #form1[action="admin.php?page=events"] a.button-secondary[title="Export to Excel"] {display:none !important;}
        </style>';
    }
}