Well, without knowing if you're talking about DDE (Disney Dining Experience) or
DDP (
Disney Dining Plan) the answer is yes.
With DDE you can purchase your card and use it for 1 year from the date of issuance on any & all trips you go to WDW. This would generally cover most sit-down (TS) restaurants and give you a 20% discount, with an 18% autogratuity added.
With DDP you'd have to make your room only ressie into a MYW package and add the dining to it. Depending upon if you're trying to do it during
free dining or not, will determine what you pay. If it's not during free dining, you should just be able to add it at cost (I believe roughly $30per adult per day for standard 1 TS, 1 CS, 1 snack per day, or $60 per adult per day for the deluxe version). During "free" dining, however, you can't just add it without purchasing at least one park ticket per person on the plan, so you'd need to purchase a 1-day park ticket for each adult you want to have free dining during the trip (a 1 day park ticket would still allow you to get the free dining even if you're doing a 2 week trip, so you'd have it the whole 2 weeks). You do not need to use the park ticket during your trip (since you'll have the AP), and they do not expire, so you can save it and apply the cost of the 1-day ticket to your AP-renewal next year.
