I disagree with Haioken, Rockstor works fine with other docker containers installed. You’re not going to see them in the main UI, but if you’re fine with that, Rockstor will run fine, assuming your app doesn’t remove needed parts 
Regarding having no WebGui, your best bet is likely to reinstall from scratch again.
Rather than using DockSTARTer I would recommend trying Portainer.
I created a Portainer rockon, and then used that to setup other docker instances.
If you want to use Portainer like I did, you can put the following portainer.json into /opt/rockstor/rockons-metastore and then install it as a Rockon in Rockstor itself.
From there, go to the Portainer UI (on the Rockons page), go to settings, and select Use External Templates and paste this into the url field https://raw.githubusercontent.com/Qballjos/portainer_templates/master/Template/template.json
That will give you access to most of the LinuxServers.io docker images.
If you want to use DockSTARTer, you’ll have to dig through it’s scripts to make sure it doesn’t mess with the docker installation itself.