I am not in NSW but my understanding is that if the roof is common property you need a special resolution but if the roof is part of your lot then it is up to what rules your OC has for approving alterations/additions to units.
I am not in NSW but my understanding is that if the roof is common property you need a special resolution but if the roof is part of your lot then it is up to what rules your OC has for approving alterations/additions to units.