Posted: 01/11/2016 at 08:40
If you live in a city, having a roof terrace garden is a luxury. Just because it's (presumably) small and not a typical one does not mean it can't be a garden.
Making a small balcony or roof terrace into a garden requires imagination so yes of course you can still be involved in the profession.
Also circumstances can dictate, even if successful I doubt that garden design pays enough to have a garden in many parts of London.