If you do the order as an OceanNow request, you just need to pay the one-time fee, though if it is a drink and you do not have the package, you do pay for the drink. If you order room service specifically, then it is the $5 charge and the extra for any drink like beer, wine, soda, etc.
OceanNow will deliver to you wherever you are on the ship, but room service is just for your room. It is a bit odd to have the room service charge if the same order can be done with OceanNow