Just yesterday I played a game where I stupidly ended up on top of an asteroid with my E-Wing. I fortunately took no damage, however my ship was perched in such a way that the right edge was off the asteroid, however right infront was a tiny piece of asteroid.
My opponent stated that I would have to roll for the asteroid hit as I was coming off it since the template would (and it most definitely would) have overlapped the asteroid.
Wanting to avoid this I posed the idea of using my advanced sensors to barrel roll off the asteroid since my ships right side was off of the asteroid.
His opinion was that I couldn't do that because I was on an asteroid and thus could not take my action at that point.
I contested that it would be unfair of that to occur since I only loose my action if I end up on the asteroid at the end of my turn or the manoeuvre template overlapped with an asteroid.
Keeping within the 'fly casual' spirit, we both concluded to let me barrel roll off the asteroid since it was an intelligent and tactical way to avoid the otherwise inevitable damage roll.
I would, however, like clarification as to the rules of using Advanced Sensors while you are on an asteroid.