Currently camera controls are a bit limited in Fusion. Specially for rolling the camera, you either roll all the time, or you constrain the camera roll to never roll.
Here's an example of the camera navigation in Cinema 4D:
1 key + Left Click = Pan
2 key + Left Click = Zoom
3 key + Left click = Orbit
3 key + Right Click = Roll
3 key + Shift + Left Click = Reset Camera Roll angle.
Please watch the attached GIF to see how the roll behaves in Cinema 4D
I think an implementation like this will come in really handy. I'm not really asking for the same key and mouse combinations (although that would be great) but at least another key combination + mouse to roll the camera.