MS Flight Simulator (2020)

The roll (ailerons) is smooth on mine. The game's response to the joystick's movement is pretty sensitive so I use a light touch.  I also have to be careful not to twist the joystick while I'm turning which is easy to do as that will cause the rudders to move. I did not adjust any of the sensitivity settings or dead zones.  Below is a screen shot of those settings.  When I move any of the axes they move smoothly on the diagonal line and each 'left / right', 'forward / back', 'twist left / twist right' moves the horizontal bar 1/2 way left or right from center which is also smooth.

Note: Make sure your movements are tied to the correct axis setting.  I had to play with this for a while until I got it right as there are so many axis settings.  The ones I listed are the ones that are working for me.

There's a myriad of control options and they can be confusing. I was going through the same thing you are - also with the rudder. Make sure you assign any controller piece that moves to a control option that says Axis. Sliders (Throttle) and the joystick movement - left, right, forward and back - as well as the twist for rudder move on an axix, hence the control names to select. Other controllers that are switches work with buttons and the hat switch.  In other words, assigning the rudder control that doesn't say axis will just give you full-on left or right - nothing in the middle. There are some great videos on youtube. This one gave me the info on the Axis-based controller assignments - and I have a Sidewinder, too.  : )  https://www.youtube.com/watch?v=pxY510tvIuA&t=270s

Fantastic!!! that worked perfectly!!!

I am experiencing that same thing.

Thanks. I had set mine up nearly identical to your setup lol. Unfortunately I can't roll smoothly and had to resort to an XBOX controller for now. I appreciate the response😎