The WordPress Codex has a function called ‘wp_list_pages.’ What I wanted to do is create a new function called ‘wp_list_main_pages.’ So I simply searched my WordPress install and copied the ‘get_pages’ and ‘wp_list_pages’ functions and pasted them into my theme’s ‘functions.php’ file. From here I made a few edits to these functions. To start with, I renamed them ‘wp_list_main_pages’ and ‘get_main_pages.’

Below is the final code I’m using to display the main navigation accross blogs. I made notes in bold to help. Hope this is helpful to you Googling coders.

// You can use this function instead of 'wp_list_pages' in your theme
function wp_list_main_pages($args = '') {
	$defaults = array(
		'depth' => 0, 'show_date' => '',
		'date_format' => get_option('date_format'),
		'child_of' => 0, 'exclude' => '',
		'title_li' => __('Pages'), 'echo' => 1,
		'authors' => '', 'sort_column' => 'menu_order, post_title'
	);

	$r = wp_parse_args( $args, $defaults );
	extract( $r, EXTR_SKIP );

	$output = '';
	$current_page = 0;

	// sanitize, mostly to keep spaces out
	$r['exclude'] = preg_replace('[^0-9,]', '', $r['exclude']);

	// Allow plugins to filter an array of excluded pages
	$r['exclude'] = implode(',', apply_filters('wp_list_pages_excludes', explode(',', $r['exclude'])));

	// Query pages.
	$r['hierarchical'] = 0;
	// Right here we call our new 'get_main_pages' function
	$pages = get_main_pages($r);

	if ( !empty($pages) ) {
		if ( $r['title_li'] )
			$output .= '<li class="pagenav">' . $r['title_li'] . '<ul>';

		global $wp_query;
		if ( is_page() || $wp_query->is_posts_page )
			$current_page = $wp_query->get_queried_object_id();
		$output .= walk_page_tree($pages, $r['depth'], $current_page, $r);

		if ( $r['title_li'] )
			$output .= '</ul></li>';
	}

	$output = apply_filters('wp_list_pages', $output);

	// This line is sloppy and needs improvement.
	// You have to remove the name of the blog your currently on from you global navigation.
	// I'm doing this the simplest but least scalable way here.
	$output = str_replace("pressroom/", "", $output);

	if ( $r['echo'] )
		echo $output;
	else
		return $output;
}

// This is essentially a private function
function &get_main_pages($args = '') {
	global $wpdb;

	// This is the magic line.
	// Now when the SQL runs to pull your navigation pages, it'll use your main blogs ID.
	$wpdb->set_blog_id(1);

	// Notice here I call the original get_pages function and return the results
	$pages = get_pages($args);
	return $pages;
}