Are There Roon Ready I2S Streamers?

I believe the K50 list did increase to $17,500.  The Antipodes K22, however, also has I2S output and list price for it is $9,000.  If interested in Antipodes, you could also consider the S Series, which are separates as opposed to all in one box for server, player, and power supplies.

Key is matching streamer to dac, purchase as package. Lots of nice dac's with optimized usb boards, which means quality clock, dedicated power supply, galvanic isolation all within dac, in this case optimized usb rendering from streamer and you're covered.

The problem with I2S is twofold, one is no standardization of pin outs or connectors, two, no conclusive evidence I2S superior to optimized usb. It would be a rare case where one could directly connect a streamer to dac without need of some conversion of pin outs via dip switch or custom built I2S cable.

Thank you all for your help.  I didn't mention that the MA-12000's DAC died over the weekend and that started me down this path.  I also have called McIntosh.

I purchased a Holo Audio May KTE and Timbernation maple equipment stand.  When I'm close to delivery, will probably pickup 0.75M Audioquest Earth balanced interconnects and the Shunyata  Sigma v2 NR power cable.  Power conditioner and good power cables have been the biggest improvement to my system.

As a long time experienced streamer, I agree I have found no issues of late using USB 2.  I’ve found some devices may default to usb 1 and must be switched manually. 

I spent several years on my search for a top quality separate streamer to pair up with my DACs. As I went through this journey I ended up with a PSaudio Directstream DAC. This was my first DAC with I2S input. I tried various combinations of streamers with Matrix Audio X-SPDIF to get I2S to my DSD DAC.

I discovered Musica Pristina about a year ago and purchased the ACapella III  I2S streamer. It was like opening a window to full transparency.  This streamer is better than anything I have tried, even at twice the price! AndKevin the designer is a joy to deal with. 
Give it a try.