The thing about roundabouts, they were a no-brainer for me here because I'd not done them in the US, so I wasn't in the habit of which way to go, whom to give priority to, etc. (I did notice that after I was in the UK for a while, then going over to France for a visit, approaching that first roundabout off the boat totally freaked me..."Which way do I go? Waaa!")
For me it's the traffic lights. There are poles on both sides of the road, and their instruction is for each lane, left or right. I wasn't used to that. One side has a red light and a green arrow, the other has a red...no wait, it's red AND yellow...what on earth! Stop changing! What do you mean? Can I turn or do I have to stop...wha...? (You have just witnessed the failing of my first driving test.)
As for left vs right, no probs. When you move here, it's to unfamiliar surroundings, and you get used to the view very quickly. In other words, when you drive on the left in an area that you become used to, it will feel odd to suddenly drive the same road on the right. You just adapt. The confusion comes when you are in an unfamiliar parking lot and about to leave. Which side of the road do you turn on to?
Also, be aware of when you are a pedestrian. You may think your coast is clear to cross a road, because you looked one way and then the other. Get in the habit of looking one way, then the other, then the first way again. I think it's fair to assume that you will never get it right in just two looks.
I had the pleasure of driving a left-hand drive car in this country. Now *that* is an experience.