According to mousesavers, there is a $50 fee.
http://www.mousesavers.com/disneyresorts.html#roomonly
* When booking through WDTC, even a "room only" reservation is considered a "Basic Plan" package (because Disney will add on some kind of small "extra" such as mini-golf tickets) and is subject to the rules for packages:
* You must pay a $200 deposit ($100 for Disney Club members) within 14 days of reserving your package.
* Final payment of the entire remainder is due 45 days prior to check-in (21 days for Disney Club members). You have to pay in full right away if you are booking less than 45 days in advance (21 days for Disney Club members).
* You can change or cancel your reservation without penalty up until 45 days in advance (5 days for Disney Club members). From 6 to 44 days in advance, there is a cancellation fee of $100 (no fee for Disney Club members). If you cancel 5 days or less in advance, you pay a $200 penalty ($100 for Disney Club members).
<b> *Any changes that result in a rate change, such as applying a discount code, reducing number of days and/or changing to a differently-priced resort, made 45 days or less prior to arrival (5 days for Disney Club members), are subject to a $50 fee.</b>
*Beware - WDTC usually adds nonrefundable
travel insurance to your package by default. If you don't want it, tell them while you are making the reservation. Once you hang up, it's too late. You can add the insurance later if you wish, up until your final payment is due.
*Airfare added to your reservation is also nonrefundable. It's hardly ever a good deal, either. I strongly advise booking airfare separately. Visit the "Getting There" page for hints on how to save on airfare!