A "rooftop solarium" is a place on the roof of a building where people can relax and enjoy the sun. It is like a garden or a lounge area on the top of a building. Full definition
Probably the best feature of this apartment is the very spacious rooftop solarium with barbecue and plenty of outdoor furniture. (rentals.holiday-home-rentals.co.uk)
This apartment is very well designed to include a large rooftop solarium complete with gas barbeque and sun loungers. (rentals.holiday-home-rentals.co.uk)
While you stay in, you can enjoy a sparkling swimming pool, a lovely sun terrace with sun beds and umbrellas as well as a rooftop solarium with Jacuzzi if you are feeling a bit more fanciful. (loveholidays.com)