Is there a way to do the rollback in cumulative update , In fact the problem is that the installed CU is SharePoint foundation on SharePoint server . any idea ?
There is no way to uninstall the CU from SharePoint. You have to rebuild the farm and restore from the backup.
But in your situation, you dont need to worry, simply install the SharePoint server CU on top of Foundation everything will be ok. You will be safe.
On side note, SharePoint Server bits include the SharePoint foundation binaries in it.