quite tricky indicating on roudabouts - if you're talking about proper big ones, you're turning left when you start; so if you put on your right indicator, what's it mean? You're going straight ahead, turning right, just changing lanes? Plus when you do change lanes it's likely to be at quuite short notice and you may not have time to change indicators too. So I'm inclined to give other drivers the benedit of the doubt and just drive carefully.
It's the ones at ordinary intersections who have no excuse at all for not indicating - they're the ones who annoy me.