Yes, if you are currently a Passholder (or have the voucher to redeem when you reach WDW), you can log onto the Passholder section of
www.disneyworld.com (click on the "passholder" link near the top right of the page). Once you log in, click on "special offers" and then the resort room discounts are under "resort offers". You can book online (although I do believe the cancellation policy is like that of packages when doing so - 45 days), or call CRO.