The person and responsibility role assignment is registered with the link between the service and the person. To edit the roles, do the following:
Right-click a person in the 'Assigned Persons' reference catalog and call the 'Edit Link' context menu action.
The 'Person Assignment to Service' editor opens. It can be used to change the assignment properties. Regarding the assignment roles:
Select another person role in the 'Role' drop down field
Add or remove one or more responsibility roles in the 'Responsibility Assignment Matrix' reference catalog at the bottom of the editor.
A user receiving different person and responsibility roles
Click 'Ok' to finalize the changes. The changes will be reflected in the Assigned Persons' reference catalog of the service template or service instance editor.