Green roofs do need more support. But think of it by percentages. A one-story house is going to need significantly more structural stability than a normal house if it wants to support a green roof. If your building is already built to support 10-20 stories, the additional weight (and cost) of the green roof and the reinforcement underneath is not as big a concern.
Personally, I would prefer solar panels on roofs and green spaces on the ground where the public can enjoy their benefits. But more green is better than less.
Green roofs do need more support. But think of it by percentages. A one-story house is going to need significantly more structural stability than a normal house if it wants to support a green roof. If your building is already built to support 10-20 stories, the additional weight (and cost) of the green roof and the reinforcement underneath is not as big a concern.
Personally, I would prefer solar panels on roofs and green spaces on the ground where the public can enjoy their benefits. But more green is better than less.