In a foreman/ovirt provisioning setup, when trying to create hosts via hammer, the datacenter, the hardware template and the network id that has to be used so the command succeeds are the id's provided by ovirt's api as opposed to the foreman's api ids. A typical creation command looks like this (I scrambled the ids):

hammer -v host create --name=testhammer --medium-id=7 --subnet-id=9 --hostgroup-id=6 --environment-id=10 --architecture-id=1 --domain-id=10 --operatingsystem-id=2 --compute-resource-id=5 --partition-table-id=1 --compute-attributes="cluster=99408929-82cf-2dn5-a532-9d998063fa95,template=a0aee259-210e-49f0-a34v-33a201572142,start=1" --interface="name=NIC1,network=d2990bc8-d963-37gt-9af0-6792843c9e57"

The computer profiles ids aren't accessible from foreman's API either (v1 or v2).