I have given other names of the roles I have currently but the instructions I am giving you can change for your roles.
You can create a static where you will have all the roles you need to do all your operations. I am creating a static for you to not compare or use hardcoded values.

After that, you just need to pass to the radio group the variable that has a identifier of type Role (name that I give to the static).
Why? Because when you click on one of the radio buttons you will get the value clicked of the static.

After that when you save, you just need to grant the role for the user that you are creating.

But for your case. you need to create first the user, and then after you have created the user you need to get the id of the user that was created and put in the input of the grant role action.

Please try to do things step by step, if you have any doubts, please question.
Kind Regards,
Márcio