What do you have for configuration parameters:
2033 Allow All Roles for Requestor
2034 Requestor Role Restriction Attribute (applies if 2033 is set to YES)
2044 Display profiles in Existing assignments, My Profile and Model user
Have you run a full synch on the roles and users since uploading roles, etc? Not sure if your original comment was a full object repository sync or a delta synch for roles
Can you try and scroll down the list to see if any roles are selectable (your screen shot suggests the Model User has more roles assigned than what's showing. It could help to see if any is selectable - such as system).
Finally, have you checked the authorisations necessary for Model User? (Object GRAC_ROLEP for Activity 78 for the connector the role belongs to). The warning message on my system is "Roles that are coming as disabled are not being maintained in ERM or for which USER don’t have the connector authorization"