What part did England play in the Seven Year War?
England played a major role in this war. Although many countries of Europe were involved in the war, England was one of the two strongest countries -- they and the French were the superpowers of those days and so the war ended up being a war of England (and its allies) against France (and its allies).
So, one way to answer this is to say that England played the part of one of the two major combatants in this war. You could also say that England played the role of the winner. This is because England and its allies ended up defeating France and its allies. Because of this, England ended up as the major colonial power in the world after this war.