We currently writing rootCA to disk via this template: https://github.com/openshift/machine-config-operator/blob/master/templates/common/_base/files/root-ca.yaml 

Nothing that we know of currently uses this file and as it is templated via MC, any updates to configmap(root-ca in the kube-system namespace) used to generated this template will cause a MC roll-out. We will be updating this configmap as part of cert rotation in MCO-643, so we'd like to prevent unnecessary rotation by removing this template.