How to hide language selector dropdown on node add page for a role?
Don't use jQuery for this. Better use hook_form_alter.

Check if user has target role.
Print out your $form and find language select in printed array.
Than hide language select.

There are 2 options for hiding:

1st:

$form['language']['#access'] = FALSE;


2nd:

$form['language']['#prefix'] = '&lt;div class="element-invisible"&gt;';
$form['language']['#suffix'] = '&lt;/div&gt;';