/* For Change Limit Size File Uploads */
function increase_upload_size_limit() {
	$user = wp_get_current_user();
	$roles = (array) $user->roles;

	if ($roles[0] == 'administrator') {
		return 1048576 * 15; // 15 MB
	}

	if ($roles[0] == 'editor') {
		return 1048576 * 4; // 4 MB
	}

	if ($roles[0] == 'author') {
		return 1048576 * 4; // 4 MB
	}
}

add_filter( 'upload_size_limit', 'increase_upload_size_limit', 99 );