Recognizing the relevance of securing inter-domain routing to protect traffic flows in the Internet, the Internet Engineering Task Force (IETF) standardized the Resource Public Key Infrastructure (RPKI), a framework to provide networks with a system to cryptographically validate routing data. Despite many obstacles, RPKI has emerged as the consensus to improve routing security and currently about 50% of routed IP address blocks are part of the system. The Regional Internet Registries (RIRs) are in charge of allocating address space in five different geographical zones and play a crucial role in RPKI: they are the roots of trust of the cryptographic system and provide the infrastructure to host RPKI certificates and keys for the Internet resources allocated in their region. Organizations and networks wanting to issue RPKI records for their address space need to follow the process from the RIR that delegated their address space. In this paper, we analyze the RIRs’ implementation of RPKI infrastructure from the perspective of network operators. Based on in-depth interviews with 13 network engineers who have been involved in their organizations’ efforts to adopt RPKI, we examine the RIR initiatives that have or would have most supported RPKI adoption for different types of organizations. Given RIRs have independently developed and implemented the cryptographic infrastructure as well as the tooling to issue and manage certificates, we offer recommendations on strategies that have encouraged RPKI adoption.