There is a long thread here : https://community.roonlabs.com/t/roonbridge-on-volumio-raspberry-pi-image/10170/24
Quick Start:
log into your pi using your ssh app (terminal on os x) and run the floowing commands. Password is volumio
enable ssh http://yourRpiIP/dev
ssh volumio@yourRpiIP
sudo apt-get update
sudo apt-get install bzip2
curl -O http://download.roonlabs.com/builds/roonbridge-installer-linuxarmv7hf.sh
chmod +x roonbridge-installer-linuxarmv7hf.sh
sudo ./roonbridge-installer-linuxarmv7hf.sh
Optional Volumio confguraiton
Set Player name so in your router DHCP leases the Rpi has a relevant name
Turn off Volumio serices: UPNP, Shairport, DLNA
Having said all this I would still like to get RoPieee working as it runs in memory and therefore immune to SD card faliures for the most part.