Anyone can request that a meal be served in their room, disabled or not. Of course if you have a less than enthusiastic attendant you may get some odd looks if you're not disabled. But most will comply without comment.

Do understand however that taking meals in your room does put an extra load on the attendant and you could find that it takes a while to get a meal and then get it cleared away. As again, they do have many other duties, the most important of course opening the door at station stops. And sticking your tray out in the hall for others to fall over is not an option, unlike many hotels where people do that.

I for one highly recommend taking at least a few of your meals in the dining car, even if you decide to have a few in your room.