[Grammar] roles v.s. role?

savemyenglish said:

They will certainly be the first to help children learn what is important in life, how they are expected to behave and what role they will play in their world.

Why "role" instead of "roles" here in above sentence? Should "they" have different kinds of "roles" to play?
Thanks in advance!

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Raymott said:

No, the sentence is fine. "They will all play a role." Each of the roles will be different, but each child will play an individual role.
Using "roles" in this context would suggest that each child would play multiple roles (which they could, but that's not what the writer wanted to say).

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