Neither is idiomatic.e is an idiomatic version.

It represents a change in China' role in the Middle East.

The repetition of "in" is grammatical. If it bothers you stylistically, you can try

It changes China's role in the Middle East.

If you are really talking about symbols, so "represents" is necessary, you can try

It represents China's changed role in the Middle East.

It represents a change in China' role in the Middle East.

is idiomatic. If the repetition of "in" bothers you stylistically, you can try

It changes China's role in the Middle East.

If you are really talking about symbols, so "represents" is necessary, you can try

It represents China's changed role in the Middle East.

Edited to correspond to the edited question.