Wix Headless : Assign role to newly registered user

Question:
How to assign role while registering member using rest api?

What are you trying to achieve:
I am trying to assign role to a member I just created using rest api.
What have you already tried:
Using wix headless rest api for custom login, I created a new member, but there is no option to assign role in register api, how can I assign role to the user?