You must book a ticketless room/dining package for annual passholders to avoid the ticket purchase requirement on a package reservation. You can apply an AP room discount to these packages if one is available.
You don't need to have the annual pass at the time you book, but you must present one adult annual pass at check-in. Only one adult has to have the AP, and you can't use a child's AP.
If you already have a room only reservation, this will make it a package. You're then subject to the deposit, cancellation and change rules for packages, not those for room-only reservations (for example, minimum $200 deposit at booking, payment in full due 45 days before arrival, cancellation fee for cancellation after that time, etc.)
You can't get free dining without paying rack rate and purchasing at least 2 day base park tickets for each guest age 3 and over, so free dining isn't available on the ticketless packages.