Solved my problem...
I have been using a third-party plugin called JHackGuard from SiteGround for security purposes. When I turn it off and add my custom php.ini, RokGallery is again working.
extensions.joomla.org/extension/jhackguard
Apparently, the extension is what has been rewriting the custom php.ini.
Nevertheless, it is time I moved to another host. Thanks for the two links there...