One person could play both roles depending upon the size of the project.

根据项目的规模不同，可以让一个人同时担任这两个角色。

youdao

I'd only make one point in the toddlers' favor: they had learned to play a game where both they and the experimenter had clear roles. The child helped out, and the experimenter gave him a prize.

对此，我还是要为那些学步儿童说句话：他们已经学习到如何玩这个游戏，无论是他们还是实验者都有很明确的角色，孩子帮忙，实验者给予奖励。

youdao

It was also one of the first times I really started thinking about some of the ways that moving overseas has liberated me and helped me break out of the roles I used to play without much thought.

那也是我头一次真正开始思考，移居国外在某些方面解放了我，帮我突破了以前习惯扮演的角色。

youdao

So realize you don't have to get it right the first time, but you have to listen and watch to what actually those problems are and that is one of the roles your teaching fellows play.

请认识到，并不是要你第一次就把事情搞对，但是你必须听听，看看,问题是到底什么，这也是你们的助教,扮演的一个角色。

哈佛公开课 - 计算机科学课程节选

Mr Verma has also pulled off a coup of sorts by signing up Amitabh Bachchan to play one of the roles - Bachchan had acted in the original.

BBC: Don is a slick upgrade of the original 1978 hit

She went alone when Rendall Harris was to play one of the lead roles.

NEWYORKER: A Beneficiary

According to the political-science literature, one of the key roles that political parties play is helping us navigate these decisions.

NEWYORKER: Unpopular Mandate