That's a terrible picture will nothing to indicate scale but assuming those brown capsule looking things are about 1/4 inch long that looks like fly pupae. Is the location near trash can or compactor? Had you previously noticed maggots?
Yep, and @[email protected] if they're hollow, they're living out their adult lives elsewhere (likely in the building). These are just signs that they used it as a pupation site.
Cool entomological fact: Cockroaches and termites (and also praying mantises) are really closely related, and many cockroaches have the ability to digest lignin, aka wood, just like termites