Add the user role to the body class
Here's how you could achieve that:

function YOUR_THEME_preprocess_html(&amp;$variables) {
  // The getRoles() method will return us the machine names, so there is no
  // need to process roles names additionally. However, I suggest prefixing
  // the names with "role-", so it's more obvious.
  foreach ($variables['user']-&gt;getRoles() as $role) {
    $variables['attributes']['class'][] = 'role-' . $role;
  }
}


Then in your html.html.twig file you can set the attributes this way:

&lt;body{{ attributes }}&gt;


Note: you might want to pass TRUE to the getRoles() method, if you want to exclude the locked roles (anonymous and authenticated). You can read the docs on this method here.