Hello
Thank you for your inquiry and I am happy to assist you with this.
This means that the memory_limit of 128M is being exhausted. There is no particular reason why this happens with the role other than Administrator.
What you should do is to increase the memory limit
To increase the PHP memory limit setting, edit your PHP.ini file. Increase the default value (example: Maximum amount of memory a script may consume = 128MB) of the PHP memory limit line in php.ini.
memory_limit = 256M
Alternatively, you can edit your .htaccess file (Not recommended see: Apache Performance: Disable .htaccess)
php_value memory_limit 256M
If you don’t have access to these files or lack the experience to make this change, you can contact your web host and ask them to increase your PHP memory limit.