To run:

ssh-keygen -f id_rsa -t rsa -q -N ""
heat stack-create -f rpc_multi_node.yml rpc -P "key_name=<keyname>;rpc_version=<branch/tag>;cluster_prefix=<prefix>" -t 150

(Replace <keyname> with your nova key, <branch/tag> with the desired RPC version to deploy and with the prefix to use in all the instances)

Failing to specify -t 150 will result in the stack-create timing out and failing as a result.