Correct Usage of "Rolls" in a sentence

Hi, I'm preparing a statement of purpose for graduate school.

I'm trying to explain my work experience at a research lab. Here's how I put it:

"I was put on rolls at the materials mixing lab, composition analysis division and testing lab of Dupont, where..."

I mean to say that I was asked to work on those 3 labs before I was permanently deployed to a specific lab.

How should I put it? Is the usage correct? Clear?

You could maybe instead use the phrase on duty as in:

"I was put on duty at the materials mixing lab, composition analysis division and testing lab of Dupont, where..."

on rolls sounds right to me though; it makes sense. However, I'm not completely sure if it is acceptable in formally written English.

Yeah? Thanks for getting prompt response!