表示“……的角色”可用“the role of ...”，一般不在其后面所接的名詞前加冠詞a/an。He will appear in the role of mediator.他會出庭，充當調停者的角色。
role用作名詞的用法例句
The Panama Canal has played a very important role in transportation.巴拿馬運河在運輸上起到了非常重要的作用。
The key role of the teacher in the learning process should not be neglected.教師在學習中的關鍵作用是不該忽視的。
The role of the railway declines in the transport system.在運輸系統中,鐵路的重要性逐漸下降。