I prefer to take roundabouts in primary (centre of the lane), following the road signs or arrows on the road surface, which will hopefully give me a easily predictable route through the roundabout.
http://www.britishcycling.org.uk/co...ctive-Traffic-Riding---Part-3---Roundabouts-0
So in your case, if the right hand lane was to go straight on, I would take the right hand lane in primary until I had successfully completed the maneuver through the roundabout.
So, for example, this roundabout, I make sure I communicate and give plenty of shoulder checks, and go around like this:
I take the third lane (in primary) ready to join it
http://goo.gl/maps/x1OCD
http://goo.gl/maps/sHrfi
Take the lane (in primary) on the roundabout posted A1400 Gants Hill (as that is my destination)
http://goo.gl/maps/Ys32U
Then I continue in my lane (in primary), which now becomes the centre lane, again for the A1400 Gants Hill (as that is my destination)
http://goo.gl/maps/Kv0bK
I then continue in my lane (in primary) as it then becomes the left hand lane, and signal left where the island is
http://goo.gl/maps/mTObj
I then exit here (in primary) and get ready to move to secondary
http://goo.gl/maps/q1NHW
For me this is a big roundabout, and I like to make sure I make my self visible.