I was on a DEN-IAH flight where the gate agent kept telling me she "didnt know the details of why the flight was delayed and that they were sorting it out". The plane sat at the gate for nearly 2 hours with "unknown issues." Everyone eventually boarded.. then after about 30mins of being seated, the pilot announced that we were de-planning due to COCKROACHES. That was quite disgusting and embarassing for UA at the same time.