I'm not sure which is worse - your posting of the images, or my admitting to knowing what they are and refer to...
Perhaps it's Bono's intention to use the flying saucer as a stage of epic proportions, only this time with the U2 Tower as a backdrop instead of the Central Bank?
I'm not sure if I'm joking...
The Clarence as currently stands is quite an odd building with regards height - it'd remind you of the 19th century fashion on Sackville Street to build tall awkward buildings on narrow plot widths. Saying that, I cannot imagine much of the rooftop storeys to be orginal, especially given they're all clad in modern pre-patinated copper, and the angular portholed sides are reminicent of an 80s apartment complex (like at the Swan Centre to tie in nicely with above
Was there ever a penthouse storey up here before the 90s renovation? Again probably unlikely given that great chimney there to the side... Any pics? Indeed the more you look at it, it seems likely the mellow slates were simply salvaged from a former pitched roof on the site.
That's not to say it still doesn't have a certain character; if anything the upper floors are quite elegant in a quirky way, but as often the case with such buildings, the upper side elevations are cumbersone and ugly, treated as secondary elevations even though they're just as visible as the principal. Needless to say, the air-con conduiting also does them no favours.
In this respect, I'd imagine none of the rooftop is protected, so they could sweep it clean off quite legitimately.
Here's their website, with a few insights as to interiors - the foyer, Study and basic structure of the Tea Room seem to be intact.