To test that it is working, use your desktop browser and go to http://(ip address of your Pi):8080
To have it show up on the Pi, I use Chromium (open source upstream for Chrome) with a custom systemd unit file and a custom script. More details here: Roon Extension: Roon Web Controller v1.0.0 (on GitHub)
This is provided as-is. It might work, but you will have to tweak it for your system and it comes with no warranty.