Roundabouts have the unfortunate property of smoothing throughput from a sequence of chunks and gaps to a constant dribble. That's fine on limited access roads

Roundabouts have the unfortunate property of smoothing throughput from a sequence of chunks and gaps to a constant dribble. That's fine on limited access roads with overpasses and parallel feeder roads for local traffic or where overall throughput is always low enough to still comfortably cut in from a lower rank junction. On everything in between (enough traffic to make turning difficult, but still having direct junctions with access roads) you are better off with the occasional traffic light that will as a side effect serve gaps to meet rank junctions downstream.