What is imagery in a play?
a figure of speech that makes a comparison between two different things
a literary device that uses vivid language that appeals to the senses
a figure of speech in which objects, such as trees, have human attributes
a literary device that uses things like animals to express abstract ideas

A literary device that uses vivid language that appeals to the senses

Explanation:

In literature, imagery is a vivid and descriptive language that evoke in us pictures or ideas that appeal to either of our five senses: sight, hearing, smell, taste or touch

An example of a sentence using imagery is "I had never seen Andy’s room this dark, messy and stinking.", the words "dark" and "messy" appeal to our sense of sight, while "stinking" appeal to our sense of smell.

a literary device that uses vivid language that appeals to the senses

Explanation:

i may be wrong but i think your answer is flashback

cockroaches and rats often are a symbol for things that are disgusting or vile. though i don't know which play you are talking about, i hope this !