You may encounter this warning when the workset you are editing is no longer valid due to changes in the central model.
Warning: The central model has been restored from a previous backup. As a result, the following workset(s) edited by you have been rolled back.
Issue: You had a workset editable by you in this local model. Another user has replaced the central model with a previous backup copy, where the workset you are editing either does not exist or has a previous version.
Solution: Find out why the central model was restored. If it must stay restored, you have to redo your changes again after making another copy. You can copy elements from your current local copy, if that is helpful.