Before you get started with either your balcony garden or gardening on your rooftop, there are some very important factors to consider.
Firstly, and of course the most obvious, make sure that the structure can withstand the weight and the rooftop will not be comprised with anyone walking on it, let alone creating extra weight or watering difficulties.
Most apartment and condominium balconies will definitely support gardening in containers and planters. The ones that are built with wood may not support extremely large and heavy pots; however, gardening can still be done with smaller planters. Where you have concrete floors, there is little damage to the surface, however, be sure to avoid using very heavy containers. This is where research into other planter materials is prudent, your resin garden planters do not contribute weight in of themselves and larger containers therefore may be used. Spread the load over a wide area using wooden slats, brackets and hooks to take the weight of hanging pots or baskets.
Secondly, check the microclimate of your balcony or rooftop. Note the direction of the wind and how much sun it gets during the day. Some balconies are very sheltered and receive no direct sunlight; others are fully exposed and take the direct sun all day. Of course, the rooftop garden may be sheltered by service structures or you may place your own trellis to give some protection from the wind and sun. Many balcony plants do not get much rain because they are situated under an awning or protected from the balcony above. In this case, make sure that the containers are kept moist by watering daily.