No, the rooftop bar is not serving food yet -- they are still figuring things out. Perhaps in a few weeks. You cannot reserve a table, it is first come, first served, even for hotel guests.
The bartenders don't seem very experienced. I asked a bartender for a specific recommendation regarding cocktails and he said, "I don't really know, I just drink beer." Another bartender -- quite young-looking -- was measuring the ingredients for a basic cocktail with a jigger. Also, at the moment the spirits available are of the lowest common denominator. It seems they don't have a "top shelf".
Glass of wine (served in a plastic replica of a wine glass) is $9 -$19. Basic cocktails are $16 (e.g. Moscow Mule - Smirnoff vodka, ginger beer, lime juice). Amstel Light is $7. Brooklyn Lager is $8
However, the view is great, seating is nice and it's a beautiful place to hang out.