If you want container plantings on your roof deck, water is a must. A licensed plumber should be able to "tee" into your apartment's water supply and extend a line through to the exterior wall of the roof deck, ending with a hose bib. If it's new construction I would expect this to be fairly simple. Including a shutoff valve may be helpful in case you ever need to service the outdoor portion of the system separately.

Thank you, Verdance!