I also have this issue, and have found no fix. Same symptoms - audio completely gone in-game. Can go multiple days without occurrence, or can happen multiple times in the same day. Changing default audio device, unplugging/plugging back in device do not work - only 'fix' is restarting the game. Happens most frequently in MSQ roulette for me as well, but has also occurred in other roulettes (occurred this evening in level 50/60/70 roulette).