You cannot order a bottle of scotch for your cabin.
When it comes to the scotches they have at the ship's bars you can expect most of it is blended. However I just returned from the Oasis Of The Seas and while I am not a scotch drinker I did see the following at a couple of the bars: Glenfiddich 12 year, The Glenlivet 12 year, and Macallan (but I don't recall the age). Royal Caribbean tends to have the same bar stocks across the fleet so I'd anticipate finding the same brands on your cruise.
You will probably find a larger selection of scotches at the pub in the Navigator's promenade.