The example seed file suggested fails under Rails 4 RC1 with the following error and a stack trace:
Could not find table 'name'
I converted:
Role.find_or_create_by_name({ :name => role }, :without_protection => true)
to:
Role.where(:name => role).first_or_create(:without_protection => true)
Now it seems to work great.
Note that I did switch from find_or_create to first_or_create, which seemed more explicit for this context.