The Costanera Center is the best future bet for such facilities. The tower itself is still under construction. It will be 300 meters high and South Amarica's tallest building. It seems likely that it will at least have an observation platform of some kind.
Currently available are several apartment hotels with rooftop swimming pools and lounges. You would of course have to stay in those locations to take advantage of the facilities. I stayed in a hotel where the breakfast lounge was in the 17th floor. 17th floor just don't impress much in this city.
Rather on random I found a hotel named W Santiago (link to a Tripadvisor review) which looks like it has relevant facilities. I have not been there myself, but the reviews are good and pictures indicate a very nice rooftop pool. I do not know if there is a general access restaurant.