One of the things that was clarified with the IANA Stewardship Transition is that ICANN has (at least) two distinct roles contained within it: one is coordination of the domain name community to develop Domain Name policy and the other is the IANA / Public Technical Identifiers (PTI) role serving as operator of the IANA functions (i.e. performing the administration of the various DNS, protocol registries, and the Internet numbers registries)
The IANA doesn’t set policy, but rather takes policy for each set of identifiers from the respective community: a) ICANN DNS Community for the DNS root zone, b) IETF for the protocol parameter registries, and c) the RIRs for the unicast IPv4, unicast IPv6, and ASN registries listed in IETF RFC 7249. David is definitely correct to say that determining what (if any) governance model should be utilized for the root server operators is a question outside the scope of the administrative/technical operations performed by the IANA/PTI, and rather a question that the various DNS stakeholders (DNS community, ICANN, IETF, and the Root Server Operators) must ponder.