score:7
That's a bit risky, since the roll is only held there by pressure. A couple of good whacks to the side, exactly like the ones the bag will receive on the conveyor belts and in the loving arms of the baggage loaders, and it can be knocked out.
There's a simple trick for considerably increasing the odds of a rucksack and its attachments making it through in one piece: just pop the whole thing in a giant garbage bag, preferably a reasonably heavy-duty one. This also prevents straps, zippers etc from getting caught, and as a bonus makes theft from your bags harder as well.
Some backpackers improvise by using the pack's integrated rain cover, but this usually only covers half the bag, may get pulled off by accident, and is usually no good for securing attachments.