Snippet for https://formidable-masterminds.com/conditionally-require-fields-by-user-role/

conditionally-require-field-by-user-role.php

<?php
add_filter( 'frm_validate_field_entry', 'conditionally_require_a_field', 10, 3 );
function conditionally_require_a_field( $errors, $field, $value ) {
	if ( $field->id == 25 && trim( $value ) == '' ) { //change 25 to the ID of the field to require
		
		/* get the current user object */
		$current_user = wp_get_current_user();
		
		/*  */
		if ( in_array('administrator', $current_user->roles ) ) { // change 'administrator' to the role you want to make this requireed
		  $errors[ 'field'. $field->id ] = 'That field is required';
		}
	}
	return $errors;
}