Roofs sometimes have gravel or loose pieces as part of the design. But if you see tiles lying around, bits of broken brick, or chunks of previous repairs scattered and not cleared, it suggests neglected housekeeping.
Loose debris can block drains, bang around in strong wind, and damage waterproofing layers. It can also become dangerous if blown off the roof edges.
A clean roof, on the other hand, indicates regular checks and care. The presence of random junk often means “out of sight, out of mind,” which is not what you want above your ceiling.