Europe (2): RIPE and Netnod AB. RIPE is Europe’s RIR, run as a conference by European ISPs. Netnod is a Swedish ISP.
Asia (1): Project WIDE, part of the Tokyo Institute of Technology.
US (9): Verisign, Cogent, NASA, US Department of Defense, US Army, the University of Maryland, ISC (as in the Bind9 people), ICANN itself, and the University of Southern California.
The last two seem to have some overlap and there is probably a lot of overlap between all of these organisations.
Verisign runs two root servers which is why the list has twelve entries but the root servers run from A to M.