[JasonACT]

The road rules on roundabouts were changed 22 years ago (for a lot of states & territories, in 1999 apparently) and even then they (those in charge) couldn't agree on exactly what was required and left it up to the driver to decide with some vague wording.

You can sort of work it out though...

Single lane: indicate as directed on entry if needed, but since it's single lane - it'll be a small roundabout and exceptions already described mean no need to indicate out.

Dual lane: left lane = turn left or go straight, right lane = go straight or turn right. Indicate as directed, but indicate left on exit... but that's a bigger roundabout, many people know the car waiting won't be able to see a left indicator (because it's a large roundabout, and depending on the car the indicators are all on the side of the vehicle [even the front one] at that angle) so they just switch off the indicator instead.

Dual lane, but have to merge back to one lane on exit: left lane, indicate left then right to merge back. Right lane, indicate left to merge back, all good there then. What a total sham though with that part in this argument! Guys in the left lane have to indicate left and right according to the road rules.

Nuts! So they made it vague.