What does it mean to have two dragons playing with beads on the roof?

A decoration on the ceiling in traditional Chinese architecture. It is called "Caijing", which means that the five elements use water to control fire and prevent fires. They are usually placed on the Buddha's throne in temples or above the throne in palaces. It is the recessed part of the flat top, which can be square, hexagonal, octagonal or round, with carvings or paintings, the most common one is "Double Dragons Playing with Pearls".