Fill attributes with usernames

Hi!
I want to develop a course booking site. Setting up the site, products and design went flawless. But I will have to do some serious Backend development.
Heres my problem: I have an attribute ‘teacher’ which contains the name of the teacher. However there are many teachers involved (~50) and they will have their own account with certain role on wordpress. Is there a possibility to fill the dropdown for ‘teacher’ with users who have a certain role? I could do this by hand, but this would add human errors to development (misspelling,…)
Any suggestions how to solve this?