I don’t know what’s going wrong for you, but /root is the home directory of the ‘root’ account - the administrator, the superuser - and it’s not normal to install anything under there. /var/ is a good place for data which is changing, and Discourse is installed under /var/discourse. But Discourse uses the technology called docker, and that places its data under /var/lib/docker. So you should expect to see both of those.
Possibly you have read something which has confused the string “root” with the root of the filesystem, which is called “/”.