Roundabouts can be a useful form of infrastructure to slow traffic down and make streets safer. In some cases, temporary roundabouts are even constructed as a tactical urbanism project to make the argument that they can be effective and are funding-worthy.
The Transportation Research Board (TRB) provides leadership on transportation improvements and innovation through quality information exchange, research, and advice regarding all means of transportation - roundabouts included. The TRB National Cooperative Highway Research Program's NCHRP Research Report 1043: Guide for Roundabouts provides information and guidance on all aspects of roundabouts. You can find the PDF of this report on their website here; Strong Towns has also attached it (in 2 segments) to this post.