That's what I thought I was talking about, too : )
As an aside, this roll motion does not happen with turrets (obviously), nor in astronaut mode, so I won't accept "has to be that way because too complicated to explain" ; )
It's not that it has to be that way, but that space has no absolute position.
Turrets are connected directly to another object, giving them an automatic default angle plane relative to said object.
Astronauts are almost always aligned to a nearby ship, station, or planet.
So, what should a spaceship automatically be aligned to, and why?
My earlier suggestion was simply to give ships some kind of distant alignment effect that's easy to use, so you can align to a particular planet or station for easier relative docking and navigation, but in open space there's no specific direction or object to align to.
Valiant suggested a turning dead zone on the screen for navigation, giving ships a self-referential turning angle, another method might be to just add a secondary piloting mode.
From your suggestions this would involve turning Roll off unless you hit a certain key, which could work for basic navigation but would murder you in a dogfight. I don't know how hard it would be to implement but it wouldn't be impossible.