Hi,
We have landed a partial fix for this issue in 2020.1.0a17, and backports are in progress for 2019.3 and 2018.4 at the moment.
I say “partial” because it improves the situation in all cases that we know of, but there can still be some undesired roll when the camera is rolling whilst looking up/down. But for roll whilst looking ahead/left/right, you should see a large improvement.
Thanks for everyone’s patience with regard to this issue.
For anyone who is in need of a better solution, and is able to use Unity 2019.3, I would urge you to look at converting the code at Particle System C# Job System support into a Burst-compiled C# Job, because that will be very performant. I am hoping to find some time to do this myself and make it available via the forums soon.