Since you're on a custom rooted rom, OTA will not install anyway. You can however disable the ota notifications all together by going to system/etc/security folder and rename otacerts.zip "otscerts-bak.zip or whatever. Rename the file and reboot then do a prl & profile update. then check for system update once more and it should let you know that your system is up to date. That should stop the ota notifications and also the error when trying to download & install the ota. If you really want the ota then you should odin flash the stock unrooted rom and take the ota's that way. Ota's always fail on rooted custom roms.