The first non-LCSD skate park we visited happens to be on a roof.
The H.A.N.D.S skate park is built on top of the H.A.N.D.S mall in Turn Mun, a short walk from the lovely Tuen Mun Park. It's by far the largest skate park we've visited but also, oddly, the most basic. The architect for this project, Alan Cheung, was quoted in Lifestyle Asia as saying he wanted to keep the park as a community space, as opposed to a pure skate park, but I feel it's missing a trick, so to speak. It's such a lovely space and could be brimming with little ramps, rails, and even a full pump track.
What it does benefit from is a lack of LCSD staff telling everyone what not to do!
If you're in Tuen Mun, it's worth checking out but I wouldn't make a journey specifically.
Address: H.A.N.D.S Mall rooftop D. 2A Tuen Mun Heung Sze Wui Rd, Tuen Mun