...
Directly attach your USB drives to the Roon computer (preferably running RoonServer) or point Roon to a dedicated NAS box (e.g. Synology or WD MyCloud, which is what I use).
I have been listening my collection of about a dozen albums I use to compare new gear. Most recently to Steve Roach's "The Magnificent Void" and that album is a gapless playback torture test; even the slightest tick/delay in track transition really stands-out. With MPD playback of these AIFF tracks on my NAS share (WD MyCloud), gapless playback is 100% smooth.
With Roon: I am hearing subtle delays in gapless playback; adding Disksomnia to keep my WD MyCloud running helped and it’s OK, but not MPD perfect.
So, I am moving the Roon library to direct-attached storage on the Mac Mini, currently re-scanning/analyzing and will try my test albums again to see if Roon can smooth-out gapless playback with faster storage.
Meanwhile, it's been a week since I've listened to MPD playback, so while I wait... With Steve Roach, the music seems to have more "weight" to it and sounds just buttery smooth, clear and with a lot of texture. I suppose it's all expectation bias, but with my experience, so far, I anticipate returning to MPD for most critical listening. We'll see after the library update and re-try.
Playback chain: Sennheiser HD-650, HD-700, Woo Audio WA3 (tubes: West. Elec. 421a + Telefunken E188CC), Bel Canto DAC 2.5 with Audioquest Carbon AES cable from BDP-1 to DAC.