I found this bit of info on using a RB.
how to safely exit a multi lane traffic circle - Search
When approaching a multi-lane roundabout, enter the appropriate lane well in advance of the intersection. Once you find a gap in traffic, enter the multi-lane roundabout and travel to your exit. When you leave the traffic circle, use your directional, watch for pedestrians, stay in your lane, and exit safely1.
In a multi-lane roundabout, you will see two signs as you approach the intersection: the same yellow “roundabout ahead” warning sign and speed signs used for single-lane roundabouts, and a black and white “lane choice” sign. This second sign is to help you choose the appropriate lane for the direction you want to exit the roundabout.
Not sure if this completely addresses the issue but it does say that the lane choice sign is a Traffic Control Device.