I ride solo through a couple of round-a-bouts quite regularly. As I approach I am riding on the road shoulder, but when I am within 50' or so I safely move in and take the lane. I ride through the r-a-b just as if I were a car. This is the safest and best way I have found. It sends a clear message to drivers of your intentions. It is also consistent with our local traffic laws, and it works very well.

This illustrates what I am talking about: