Back again, having given up trying to identify a short film (maybe 2 minutes long?) I saw on television in the early 90s (possibly on Night Flight, USA Up All Night or similar type clip show). It was in color and looked like it could have been made in the 1980s(?) It was about a family living in a desert cave years after a nuclear apocalypse. The parents are preparing a meal in a pot around a campfire and begin telling a story to the children about life before the bomb. In the story, which we see rendered as a flashback, a housewife is preparing dinner in a typical suburban kitchen, only to be frightened by the presence of a cockroach. She comically screams directly in the camera before the roach is killed off in some manner (can’t remember if it gets stomped or sprayed). Returning to the cave, the children are in disbelief that someone could be so afraid of a cockroach. Then we find out why. The food the parents are preparing in the pot is a cockroach soup, cockroaches being the only animal to survive the nuclear war.
It’s definitely NOT Damnation Alley or Twilight of the Cockroaches (which is what you are going to find when you Google for “post-apocalypse roaches”)