You cannot roll back the central models of server-based workshared projects.
While using server-based worksharing, if you select the Restore Backup command, the Revit Server Network folder does not display in the Browse for Folder dialog.
You can roll back the local models of server-based workshared projects, but it is not recommended. A limited number of backup histories are kept. Rolled back files may not be sync-able with the central server. The Restore Backup command can also be used with file-based workshared projects.