You can deploy OpenShift Data Foundation on 3 worker nodes of 10 CPUs and 32 GB RAM, but you must taint your worker nodes to run only ODF pods. You can't run any additional app workloads or system pods on your ODF nodes when you use this setup.
Why 10 vCPUs? ROKS does not have such a flavour. This is either 8 vCPU or 16 vCPU.
The prerequisites section of the ODF doc https://cloud.ibm.com/docs/openshift?topic=openshift-deploy-odf-vpc&interface=ui#ocs-storage-vpc
states the following:
Why 10 vCPUs? ROKS does not have such a flavour. This is either 8 vCPU or 16 vCPU.