You can make the request by using the contact us on the left of the page. Use general and send you request to CSS. Make sure to include your Booking number, Romance Reward number, and your arrival date.
They will do what they can to meet the request, but do not be upset if you can not get that room. You may be better at requesting a block and floor, that way they have more options.
It really doesn't do any good to request a room before hand but when you check in, request it and if it is available, they will give it to you. We have been given a room we requested once. I have to tell you, it's kind of neat to be surprised with a new room. I have liked every place they have put us.