Volume control with Pi-Digi+


I would like to connect a new DAC to my Roon environment, and so I am thinking to buy a Digi+ from IQAudio.
In this case I would have the following:

[Roon Core] ----(eth)---->[Digi+]----(coax)---->[DAC]----(rca)----->[power amp]

The question is: how can I manage the volume level in this configuration? (power amp has no knobs)
Am I able to change the Pi-Digi+ volume from Roon (as with a Pi-DAC) or do I need a dedicated pre-amp before the power amp?