The role usually implies the relationship between the teacher and learner, particularly in terms of the autonomy the learner has over their learning.
Example
Facilitator, assessor, manager and evaluator are all teacher roles.
In the classroom
Teacher roles can be discussed with learners as part of learner training, along with other aspects of classes. Learners can think about what roles they prefer for their teacher, how this preference fits in with other aspects of their learning style, and why the teacher chooses each role.
Further links:
https://www.teachingenglish.org.uk/article/jordana-mazzarotto-ana-francisca-rosada-creating-a-positive-learning-environment