Lorry's "fault" for indicating right approaching roundabout is debatable as he/she changed mind and indicated correctly left when on the roundabout. We all get lost at times and end up in the wrong lane, or realising we actually need the 2nd exit instead of 3rd... So, it's a little poor to miss the left indicating, but I know in that situation it could be easily done.
But, the lorry also exited from the inside lane on the roundabout without checking mirror - this is even more frustrating/wrong as they knew they were incorrectly indicating right prior to the roundabout, so they should have double-checked for anyone misinterpreting their erroneous signalling. He's technically changed lanes from inside to outside and then left the roundabout, all without looking. See it happening quite often when the exit from a roundabout is dual carriageway and someone on the inside lane just roars to exit, while someone on the outside lane is still wanting the next exit. Whoever is on the inside needs to check mirrors and give way to traffic on the outside, as they're doing a lane-change. I fully appreciate, with the size/visibility of a lorry, it's expected for them to take this line around such a roundabout, when going straight on - this still doesn't mean they shouldn't check when exiting tho...
I think the lorry technically did more "wrong" but experience would make a driver not to be on the outside of a lorry trailer around a roundabout and thus get into that situation. I could almost see myself doing it, especially if it's busy traffic and other cars were entering the roundabout from both lanes - if I saw him indicating right prior to the roundabout, I probably would have been beside him as he entered the roundabout. Depending on the tightness of the roundabout and whether i thought he needed to use both lanes to turn around the roundabout, I would have either gone with him or waited. But, I guess that if I had entered the roundabout at the same time, it would/should have made me a lot more visible to him, before he exited...