Services can not create an user with role I follow this answer How to create user with role(s) through REST service? 

{"name":"user343","pass":"kes35@r4","mail":"user343@sample.com","status":"1", "roles":["4"]}


But When I check the created user, It role still is '2' (authenticated user)
Just install Auto Assign Role Module.

Then use this following json code:

{"name":"user3431","pass":"kes35@r4","mail":"user343@sample.com","status":"1", "user_roles":{"6"}}