I think you need to create some code to detect the role being used ($curRole) and for end user or roles that are restricted use:
<input tabindex="1" maxlength="100" type="text" id="first_name" size="30" value="{COLLECTION/icuser/first_name/LITERAL}" disabled="true" />
and for the other roles which are not restricted:
<input tabindex="1" maxlength="100" type="text" id="first_name" size="30" value="{COLLECTION/icuser/first_name/LITERAL}" />
Hope this helps.
Regards,
Pablo