Online bookings for 2017 won't be possible until Disney releases the room rates for next year. That won't happen until sometime this summer. If you want to book a room only reservation before then, you will have to do it by phone, directly with Disney. Do your research beforehand so you will know what resorts and room categories you want. But be aware that the prices quoted will be the highest rack rates for 2016. Your deposit will be based on that and your balance owing will be modified when the new prices are announced.
If you are determined to use Orbitz or another 3 rd party site,, you just have to wait.