1) Disconnect your internet connection, to Control Panel > Network Connection > Right Click your local network and hit "disable". (or pull your network cable, disable wireless w/e suits you).
2) Launch C:\Program Files (x86)\Rift Game\riftpatchlive.exe or your shortcut.
You will get a couple of errors saying your cannot connect to patching server etc but just click ok.
3) Once your at the login screen, go back and re "enable" your internet connection.
4) Once you confirmed your connection is back (go test on google) login into the game.
It might check your local files, which might take a couple of mins. When the file checking has complete, it may download an update and patch it but then you'll be able to log in.
