In “the chickens come home to roost” - is “roost” a verb or noun?

Question

Consider:

the chickens come home to roost

Is the word roost used as a verb or noun in this idiom?

Answer 1

In this idiom, it is a verb. (infinitive phrase) and gives the reason the chickens have returned. The noun form would be:

"The chickens have come home to their roost."