Are you already running Roon? They offer a
free trial; just install it to your PC and give it a try. As you've discovered,
Roon does not yet support Deezer so you'd need to continue whatever you're doing now to play it. And of course, you'd need to buy a
subscription to continue using Roon after the trial.
If you decided to untether your PC from your DAC and instead play remotely through a Raspberry Pi, you'd have available whatever music sources are supported by your music server.
Ropieee is an end-point for Roon, so still no Deezer.
piCorePlayer is an end-point for
Logitech Media Server which
does support Deezer. Something LMS can do that Roon can't is run
as a server from an RPi. You could start by installing LMS on your PC just to get used to the way it works in your current setup. Later, add the RPi if you want and run it as both a player (feeding your DAC) and a server supporting your entire network. This takes your PC out of the picture as a dependency which some people like for the reasons you've mentioned and also because they don't like leaving their PC powered on to listen to music. You'd move any local music files to an external drive connected to the RPi or plugged into your router if it supports file sharing. piCorePlayer and LMS are both free.
Note: If you are curious about LMS, you might try the
beta version 8.0 which supports integrating music services favorites with your local music library. For instance, on one page you'd see all Allman Brothers albums available for you to play whether your own rips or albums you'd added as favorites on Deezer.