Sadly this isn't an option for UserGroup management, but there are a few ways you can accomplish this. Rather than upload a whole new showroster.php file, I'll give you the best and quickest way I can think of.
Open your SHOWROSTER template and replace it with the following code.
Code:
$stylevar[htmldoctype]
<html dir="$stylevar[textdirection]" lang="$stylevar[languagecode]">
<head>
$headinclude
<title>$vboptions[bbtitle] - $vbphrase[show_roster]</title>
</head>
<body>
$header
$navbar
<if condition="(is_member_of($bbuserinfo, 5, 6, 9, 10))">$usergroups<else /><center>You do not have permission to view this page! Turn back now or you will be beheaded!</center></if>
$footer
</body>
</html>
Update the numbers in ($bbuserinfo, 5, 6, 9, 10) to whatever usergroups you want to have access to that area. You can also upgrade the warning message to whatever you prefer.
I hope this helps.
Thanks for clicking install.