what is the advantage of having a Roon core that's not on your computer?

I started with an Innous Zenith MKII hosting Roon Core.  It wasn't powerful enough to use DSP or upscaling so I purchased a Small Green Computer sonictransporter i7 for Roon DSP w/o storage and everything worked fine.  I used it for over a year but eventually sold it because after a few choice upgrades my system sounded better w/o DSP or upscaling.  Having said that, the sonictransporter is an excellent component and Andrew's customer service is second to none. 

I had Lucas Domansky of Lucas Audio Labs design me a roon server/core from scratch.  Much improved roon performance, sound quality vs when running roon on old PC and sending it to streamer.  The skys the limit with features and so forth, but worth investing in some sort of dedicated roon core.

I have Roon running on an Innuos server, which is cable-connected to my DAC and then into my amplifier. I enjoy that it is located in my rack. For Roon I like it can be controlled from my phone that acts as remote. I like the SQ a lot.

I switched from using my Windows PC to using a NUC running Roon Rock. When I had the NUC connected over my home network (through an EtherRegen) to a Bryston streamer, I can't say for sure that the NUC sounded any better. But it was certainly a lot easier to manage since I didn't have to content with Windows updates causing issues and the Roon Rock automatically handled backups and updates.

But one big advantage of using a dedicated Roon server in a device that can built without fans is that you can have the device located next to your equipment. If you plug a USB CD drive into the NUC running Roon Rock, it will automatically rip a CD by just inserting it and add it to your library. 

I have recently rearranged my system by replacing the Bryston with a Denafrips Gaia. This isn't a streamer, but buffers and converts different digital audio signals. I moved the Roon Rock to the output side of the EtherRegen and connected it to the Gaia with USB. The Gaia is now connected to my DAC with i2s. This change made a big improvement in sound quality.

Moved Roon Core off my Innuos to an Antipodes Core and left the Innuos as the endpoint.  Lower noise, better music.

For me it was better than Experimental Mode on the Innuos with the DSP to DSD from Roon.

I also use a Denafirps Iris DDC to I2S and agree with the improvement in SQ.