I think that one can find the role of English to operate as both an act of oppression and an act of resistance in Postcolonial writing. For many Postcolonial writers, English was the "oppressor's tongue." British imperialism meant that indigenous languages were out and English was in. Schools popped up where "the natives" were taught how to speak and, essentially, "be English." English was the language that many Postcolonial writers learned in school, many times at the expense of their own indigenous language.
This is where English's role is complex in Postcolonial literature. On one hand, it is the language of the oppressor, coming at the cost of one's own original language. At the same time, it is the way in which voice is activated. To tell a Postcolonial writer who was raised with learning English that they need to go back and write solely in "their own language" acts as another form of silencing voice. Therefore, these writers use English as a way to deconstruct the English. In other words, the language operates as both representative of oppression and the resistance against it. This shows English to be a complex entity in Postcolonial writing.