The overriding rule at roundabouts is
Left lane: left turn and straight on.
Right lane: right turn only UNLESS the road straight ahead is a dual lane road. In this case you can use the right lane to go straight on.
There is NO legal way to be in the left hand lane and exit the roundabout on the right hand side.
Markings on the road override the standard rules.
For instance you cannot use the right lane to use an exit before 12 O'Clock unless there is a lane marking indicating otherwise. Except in the case where traffic conditions e.g. a queue of cars heading left at the first exit.
If for some reason the leftmost lane had a right arrow, then you would be allowed to use the left lane to turn right. Though in reality this would be a terrible design and should probably be fixed by the relevant authority.