post https://api.mediasilo.com/v3/projects//users//roletemplates/
To give a user access to a project, you need to assign them a role in that project. The permissions defined in the role template will govern the user's permissions within the context of the project.
Permissions
A PROJECT OWNER can assign role templates to users within a project they manage. A user with an account-level role of ADMINISTRATOR can assign role templates to any user in any project.