Do they mean the same thing?
1) I believe students should be the judges of teachers' performance, but rather other teachers.
2) I believe, when it comes to assessing a teacher's performance, students should take (on) the roles, but rather other teachers.
3) I believe, when it comes to evaluating a teacher's performance, students should play the determinative roles, but rather other teachers.

Or do they make sense to native speakers?

Question

Do they mean the same thing?
1) I  believe students should be the judges of teachers' performance, but rather other teachers.
2) I  believe, when it comes to assessing a teacher's performance, students should take (on) the roles, but rather other teachers.
3) I  believe, when it comes to evaluating a teacher's performance, students should play the determinative roles, but rather other teachers.

Or do they make sense to native speakers?

Answer

Number 3 sounds more correct.Remove the word 'but'.See below corrections.
3) I believe, when it comes to evaluating a teacher's performance, students should play the determinative roles rather than other teachers.