When did the curved Chinese roof first appear?

The distinctive curved roof in Chinese architecture first appeared in China approximately during the 6th century CE.1

While the exact origins of this design are not fully understood, it is widely theorized that the curve was adopted for aesthetic reasons from Southeast Asian neighbors. In those regions, houses were traditionally covered with materials such as atap (nipa palm leaves) or split bamboo, which naturally sagged and created a picturesque effect. Beyond aesthetics, the characteristic upswept eaves at the corners of the Chinese roof serve a structural purpose by helping to reduce what would otherwise be an excessive overhang at those points.1