i’d recommend a fast flowering femenized autoflower, something 60 or 70 days from seed to harvest would be great, but if your rooftop is a common area which people use to smoke/sunbathe/hangout i think someone will definitely notice it … and a 25 floor building probably has many residents so its probably a certainty at least some of them smoke weed … someone may wait and then steal your plant
i’ve ordered from this site before, this is their list of autoflower seeds which also shows height/growing time/yield, so you can scroll through and find something you like … you can also order single seeds
https://www.justfeminized.com/buy-automatic-seeds-212-c.asp?_=&sortby=price