Retrieve extra information from the CAS server

It’s already implemented; you can use the authorizer_custom_role filter. Here’s an (institution-specific) example:
https://github.com/uhm-coe/authorizer/wiki/Integrating-WordPress-Roles-with-UH-Groupings#step-4-add-your-integration-code-to-your-wordpress-theme

And here’s another example from the readme:
https://github.com/uhm-coe/authorizer/blob/master/readme.txt#L335-L355

There’s a long term plan to build a UI for this so you don’t have to use hooks, but no ETA on that one:
https://github.com/uhm-coe/authorizer/issues/75

Attribute mappings is the thing i am asking for actually, and not the custom user role.
I see that you are planning this, but not an ETA available, right ?

Correct. But you can do anything in that filter, you don’t have to modify the role. Set usermeta, etc. The CAS attributes are exposed in $user_data['cas_attributes'].