I figured this out by accident after not finding much in the forums about it, so I thought I'd post it fresh.
In wordpress, we use <?php bloginfo('template_url'); ?> to go straight to your template directory (i.e. "http://mysite.com/wp-content/themes/mytheme").
In bbPress, to go yout theme directory (i.e. "http://mysite.com/bb-templates/mytheme"), you use <?php bb_option('template_uri'); ?>