A vetlh is probably a Klingon creature that only resembles a cockroach. Maybe they're beautiful. Or maybe Klingons think they're beautiful.
There's a scene in Conversational Klingon where a Klingon and a Terran tourist are on a jitney, passing a power station. The Klingon says HoS lIngwI' wIjuS. 'IH, qar'a'? We're passing a power generator. It's beautiful, isn't it?