is it possible to assign roles to users through command line ?
One answer
You can write your own code to do that. See the snippets in the Plain Java Client Libraries. https://rsjazz.wordpress.com/2012/12/09/analyzing-a-aroject-areas-members-and-roles-using-the-plain-java-client-libraries/ shows how to read the roles, I believe one of the snippets assigns a role.