If roundabout has multiple lanes, choose your entry or exit lane based on your destination. See the picture below. For example, to:
1) If you (blue car) want to turn right at the intersection, choose the right-hand lane and also exit in the right-hand lane.
2) If you (red car) want to drive straight through the intersection (red car), choose whichever lane and exit in the same lane you entered.
3) If you (yellow car) want to turn left, choose the left lane and exit.