This is with the latest build as downloaded on 21/4/2016.
iFi Micro is capable of double the rates listed here.
My problem with the first 1.2 release was distortion on DXD playback - this has now been resolved. (yes, I did contact iFi and NativeDSD (Jonas) direct for support on this matter. Both were very helpful.
@Greg is correct. Roon supports up to DSD256 and 384kHz PCM right now.
Are you aware of a content provider where substantial amounts of higher-rate material can be purchased? That would push us to increase the numbers.
HQ Player. 
Nativedsd and 2L.no
Excellent providers!
I have not yet seen content above the maximum you support.
DXD - now supported in 1.2 - it is not listed yet under your supported formats. (IFI DSD micro supports 2xDXD, but I have not found any downloads yet in this format yet)
I can play files from 2L now with 352.8 kHz via IFI DSD Micro.
DXD is a marketing name for 32bit 352.8kHz PCM or 32bit 384kHz PCM. We just don’t use the word “DXD” on the page.
There are users of HQP who like to upsample all audio to DSD 512.
