Question

THE roles of both is interchangeable.(correct sentences)

Answer 1

Thanks for the question...

This is a very simple yet tricky riddle that involves mental aptitude. 

''''Both the roles are interchangeable'''' is the correct answer.

Hope it is helpful for you and solves your query too!

Answer 2

There are two issues with this sentence:

1.    Missing information- The roles of both …what? It could have been both the teachers or both the workers.

2.    Subject-verb agreement error- The roles of both is interchangeable. A plural subject (roles) requires a plural verb (are).

Since it is not advisable to add words on your own, the correct sentence would be

Both the roles are interchangeable.

Here, the order of words has been changed and the verb has been changed from ‘is’ to ‘are’.