So, the rules say that you "can measure to see if you can perform a barrel roll before committing to the action". Thus, if the BR would have you overlap an asteroid or ship you can do something else instead. A couple questions I have are,

If you can't do the BR you want because an asteroid is in the way, do you have to BR in the other direction?

Can you measure a barrel roll (or boost) and then decide not to commit to it for other reasons?

I confess, when I just reread the rule, it didn't say what I thought it said. What I thought it said (and how I have seen it explained here) was that you declare you are BRing, measure to see if the BR is possible, and if it is you must go through with it. If that were the case though, it would seem that you could be forced to go off in the opposite direction if your preferred direction is blocked.

What the rule actually says is (rulebook, page 8)

A ship cannot perform a barrel roll if this would cause its base to overlap another ship or obstacle token. The player may measure to see if his ship can perform a barrel roll before committing to this action.

What that text says to me is that you can measure a BR and then decide whether you want to perform it or not, which avoids the first problem but then allows people to check whether their BR will move them into or out of arc before committing to the action, which is not how I think most people are playing it.

Generally speaking, in coloquial games, you can 'test' your barrel roll, and then decide to perform another action. Players decide what are the limits of their good sportsmanship.

But under tournament rules, if you declare a barrel roll, you must commit to the action if you can.

Edit: After checking competitive play addendum, you are only forced to perform the barrel roll to the side you declared first.

If you can't perform a barrel roll to the side you declared first, you may choose another action or declare a barrel roll to the other side.

Edit: After checking competitive play addendum, you are only forced to perform the barrel roll to the side you declared first.

If you can't perform a barrel roll to the side you declared first, you may choose another action or declare a barrel roll to the other side.

Yeah, just found that myself. Not exactly the most intuitive place to put it.

Cool, good to know. Because yeah, a lot of times it's barrel roll that way or not at all as far as good options go.