Before upgrading to any release, you need to consult in the 'Update Paths - Version XX.pdf' document that is published in the Privileged Access Management product page: http://www.ca.com/us/services-support/ca-support/ca-support-online/product-content/recommended-reading/product-documentation/ca-privileged-access-management-product-documentation.html
Each Release Notes includes the Upgrade Steps for Single Appliance and Clusters for more datailed information.
This is also available in the Privileged Access Management Product Page:Documentation.
Is not possible to do a rollback. However, there are workarounds in case you need to return to a previous release:
If your PAM is installed in a Virtual Machine:
Before upgrading an CA PAM VMware VM, take a snapshot of the VM so that you have a backup in case it is later needed. CA PAM normally creates a backup automatically as a first step when upgrading a hardware appliance. However, this step is not performed during a CA PAM VM upgrade because a VM does not have a secondary drive.
If your PAM is a physical appliance:
Before applying the update, CA PAM copies its primary drive (SSD) data (including database and configuration files) onto its backup drive. If there is any issue following upgrade, your CA PAM can be restored from that backup drive to its pre-upgrade state.