There is no problem of water formation in pitched roofs, so there is no need for a drainage layer, but the soil layer where the plant roots are located is also reduced, so the vegetation layer on these roofs is low.
Sloping roofs are more likely to dry out the soil, as there is no accumulation of moisture, so special consideration should be given to the choice of plants.
The northern side would be preferable, as the relatively small amount of solar radiation received does not contribute to the evaporation of water from the soil.
The main problem with pitched roofs is the slipping of the ground layers.
Roof structures capable of absorbing shear forces must be provided.