To show a block to a one or more roles, put this code inside the block under Page specific visibility settings
Select -> Show if the following PHP code returns TRUE (PHP-mode, experts only).

Code

<?php
global $user;
$approved_roles = array('board', 'sales', 'engineer');

if (is_array($user->roles)) {
  if (count(array_intersect($user->roles, $approved_roles)) > 0) {
    return TRUE;
  } else {
    return FALSE;
}}
?>

Users with the role 'board', 'sales' or 'engineer' will see block.

Sometimes you may want to hide a block for a certain role and show it to all others.

<?php
global $user;
$approved_roles = array('board', 'sales', 'engineer');

if (is_array($user->roles)) {
  if (count(array_intersect($user->roles, $approved_roles)) > 0) {
    return FALSE;
  } else {
    return TRUE;
}}
?>