To replicate

1. Add a Delegated LDAP Directory and ensure it's below the JIRA Internal Directory in the User Directory list.
2. Create a user in the JIRA Internal Directory.
3. Add that user to some Project Roles.
4. Create a user with the same username as in step 1 in Delegated LDAP Directory.
5. Set the Delegated LDAP Directory first in the User Directory list.
6. Check that user's Project Roles - they are the same.
7. Delete the user from the Delegated LDAP Directory.
8. It will revert back to the JIRA Internal Directory user who will be missing their Project Roles from projectroleactor.

Screenshots attached from pre & post deletion of Project Roles and also an excerpt from atlassian-jira-sql.log.

To workaround

Add the Project Roles back to the user manually.