Roon for high end audio?

Roon is compatible with some of the highest end gear in the world.  

There are a variety of approaches that you can take.  It sounds like you want a Roon Server on your network that will work and talk to your Savant system and the DBX Venu360.  These will range in price from about $500 (NUC) to $35K (Taiko).  This is also where you want the most processing power as this is the part of the chain that engages the extremely volatile internet.  

The second part is the Renderer/Player.  This will take the signal from the server and get it ready to be served to the DAC. This does not require a particularly large amount of processing power.  It just needs to be a quiet device.  

Third part is the DAC.  You clearly know what that does.  

You can keep all three parts separate or many devices incorporate two or possibly all three of these features in one box.  The best devices/systems I have heard usually embrace keeping things a bit separated.  It is very common for a great server to serve as server or renderer.  I have a Weiss DAC here that is "Roon Ready" and is a tremendous renderer.  

I would probably start by picking the DAC you really like.  Depending on the DAC you choose, it may (not in all cases) dictate the optimal server/renderer. 

For example, Rockna works best with Rockna servers.  The I2S connection breaks each element of the signal out and there is a perfect synch between the clocking on the server and DAC.  The Rockna Server with a Rockna DAC will outperform more expensive products because of this synergy. 

Same goes for Playback.  The Dream DAC and their Transport are best together and greater than the sum of the two parts. 

Alternatively, a line like Chord doesn't offer a server and matching with a great server like Antipodes is the best you can do.  

I in my system, I have a standalone server (Antipodes K40) and use the renderer in my Weiss for one system and a chord 2Go/2Yu combo into an Audiobyte DAC as a bridge for the other and both are brilliant.  

Start with the DAC.  Build from there.  

I have the audio gd r7 that accepts I2S.  Using usb and very happy.  Is there an advantage to I2S.  Used hdmi cables with old ps audio transport and dac

Roon is a music interface organizer only  there is no sound improvement  
Pick a streamer that has a good interface like
Bluesound, Aurender and Auralic

Not true at all,Roon  is by far the best most music organizer out there.Qobuz, and Tidal are huge  streaming libraries to complement Roon.the key is having the quality to complement hiend streaming 
to seriously compete with discs ,or Flac files.
for example I have the latest Bricasti M3 with Streamer card option.the M3 dac and streamer is a very good example of high end sound without breaking the bank.  To complement  a direct Ethernet cable is a must,from the router is necessary. I use a decent Quality $200 Wireworld Ethernet cable from modem to router ,from router to Ethernet switch to save $$ the top professional grade 30 ft of Beldon 500 MHz bandwidth , very important here the cheap $30 Ethernet hub is worthless l use the Uptone Audio,Ether Regen 
absolutely cleans the digital noise riding on the line and from there to the streamer ,it is now clean ,and a Wireworld $200 Ethernet cable to the streamer. This is the most critical cable  I have experienced ,I will buy better in the future, and under the dac an absolute must for top clarity and resolution is a set of 4 ultra Still points. My system sounds very good . Not lacking what so ever.
sure it could be better still if I have another $5-10k.  I have roughly 
$8 k  invested in the dac cabling,power cord ,plenty good for the moment and Bricasti is at the forefront and it’s a modular design 
with the future in mind.
 

Its your gear not Roon