So I have thoroughly investigated the audio problems, tried every "fix", and here is the issue as I see it:
First try to test all components of your computer, update drivers, and perform troubleshooting steps. Next try different settings in the audio of the ROKU. If all that fails, then the following may help, though it is referring to distorted audio.
Whenever two devices connect to each other, the is a "handshake" process where each exchange information about how and what information they will communicate. Basically there is an error in how windows does this with ROKU devices. Apparently this was triggered by an update.
Now to understand what is happening, you need to know a little bit about an audio problem called "clipping". Have you ever heard a recording that you could easily hear, but was just out of wack like it had been run through some gravel or something? Go ahead and look up clipping in another browser tab... I'll wait............ Ok, now that you know what clipping is, go watch a video on youtube called "simpsons megaphone testing", its very short.
When the handshake happens between the Windows 10 computer and the ROKU, (1) if no audio track is playing, when the computer then plays audio something like the simpsons vid happens on the ROKU end, and it gets blown by MASSIVE clipping. (2) HOWEVER, if you play anything that has an audio track at full computer volume, the handshake proceeds as it should and all audio play as it should.
I tested this by creating a silent audio track that has absolutely nothing that will transmit at all, it is literally a straight line with no frequencies or wave forms what so ever. I then played it while connecting to the ROKU, and then played a video after it was connected, and the sound from it was fine. I LITERALLY PLAYED A FILE OF NOTHING AT ALL WHILE CONNECTING.
So the problem seems to be that windows needs to provide a audio sample audio during the handshake to establish what "normal volume" should be. Even if it is a sample of nothing. If Microsoft would include this as part of the process, then it seems it would fix the issue.
(AGAIN, YOU'RE WELCOME MICROSOFT!)