Steps to reproduce:
1. Create an event
2. when you enter the Access Policy Tab, you can select a Template. Select Public i.e.
3. In the field below you see 3 rows now. The dropdown for the bottom two shows the correct value ROLE_ADMIN and ROLE_ANONYMOUS. In the top row you only see "Select a role". If you continue anyway, you will see that "Select a role" has changes to ROLE_INSTRUCTOR, as expected.
This issue has been solved in Opencast 2.1