WordPress custom jquery not found

I have a custom jquery file, here is code:

/* Custom JS */
jQuery(document).ready(function(){
    jQuery("#top-menu li:first-child a").addClass('selected');
});

And here my code to load js file in functions.php

add_action('wp_enqueue_scripts', 'load_custom_scripts');

function load_custom_scripts(){
    wp_enqueue_script('custom_script', THEMEROOT.'/js/custom.js', array('jquery'), true);
}

But when i check with firebug, my js not found. Hope anyone tell me what’s wrong in my code?

https://i.stack.imgur.com/iqGdQ.jpg