Can someone explain me this… Depending on the endpoint, Roon makes a bit depth and sample conversion or not. Why is that???
show us a case of conversion and we will tell you why it’s happening.
Edwin, my guess is that the native sample rate of the Pulse Flex is 48k. This is often the case for gear designed primarily for TV use. It would then require a sample rate conversion to 48k to work which Roon detects and does. This may be an issue with a DAC miss identifying itself but I’d ask Bluesound to clarify the details of that speaker.
I think the second zone (not visible until you click the image) shows it… 
To the OP, I believe there are topics here already, covering a Bluesound issue…
Yep it’s visible,when you click on the image in the op.
For those of you interested, this problem is known and has been discussed here: https://helpdesk.bluesound.com/discussions/viewtopic.php?f=4&t=3747&sid=ecac0dd360cfd386cb03fecf8374b61e