Some Australian cockroaches definitely fly but don’t seem to do it very often. They’re quite noisy when they fly—kind of like the propeller sound you make if you trill your tongue—and there’s nothing worse than hearing that sound suddenly stop very close to you. ‘Oh fuck! Have I got a cockroach on me?’ I hate them.
Indeed and it’s quite clear that the Falcon has two gravity planes perpendicular to each other: 1. the plane that supports everyone on the main deck (cockpit, crew lounge, etc.) and 2. the gun battery gravity plane at 90 degrees. This is easiest to see in A New Hope during the TIE Fighter battle in the escape from the Death Star. Han and Luke are sitting back-to-back, separated by a short corridor that sits perpendicular to the main deck. I don’t think most people notice this because it’s not obvious.