I can reproduce this on the 4.7 demo.
I create a case of type 'Adult Day Care Referral' for client Rebekah Adams.
Using the civicrm/contact/view/case screen, I assign the role 'Health Services Coordinator' to Junko Adams. I use the 'pencil' icon to do this.
The role is assigned to Junko Adams, but the 'Assign Case Role' activity is assigned to Rebekah Adams (the client) and the subject is 'Health Services Coordinator is : Dr. Rebekah Adams'.
That's confusing, and if an email is sent to the client, that could be nasty.