There is some confusion here...
A room only discount can be applied to a room only reservation or a package reservation. There are two types of reservations:
Room only - requires 1 night deposit and balance is do (AFAIK) 3 days in advance
Package - requires a $200 deposit and balance is do 45 days in advance.
You can purchase tickets on a room only reservation. The tickets will require full payment at time of purchase, and are treated as a separate transaction. You can link them to your KTTW card when you check in. However, you cannot add a dining plan to a room only reservation.
Now, you can change a room only reservation into a package, by adding tickets and/or dining. This becomes a package and the reservation changes as noted above. Note that availability maybe different. Some had trouble making the switch and actually lost the room only reservation. (CM or TA canceled the RO, then made the package but wasn't available - tried to make the RO again and that was gone too) Technically, the room only reservation is canceled and a new package one is made. CRO will help in transferring the deposit over. You should make a new package and then cancel the RO ressie instead.
When a room discount offer (PIN, BB or public) is available, you can apply it to a room only reservation OR to a package. Again, it depends on availability. They set up certain amounts of room only and certain amount of packages.
Note there are some exception for AP holders in that under some offers, they are not required to get tickets as part of a package in order to get the dining plan. An AP veteran can answer this further.
Hope this helps clarify some of the confusion.
If you disagree, look at your reservation - if you think you have a room only one with dining, look up when is your balance due. If it is 45 days before arrival, you have a package. If it is 3 days before, then I'm wrong.