I have an object as teacher_student__c .Whenever a student is linked to a teacher, check whether the student already has a teacher with same subject assigned to him/her and if already exists, then throw an error 'A teacher is already assigned to this student for the subject.

Hi,

Is there a way I can auto populate the Contact roles on an opportuntity with a custom button based on the account name that is on the opportunity? Can I use Flows and Process builder? If so, how.

Note: Contact is not on the opportunity.