why won't passenger use the VirtualHost I set to my rails app?

Question

I'm trying to get a rails app running on Ubuntu 8.0.4. I'm actually using one of the Turnkey linux packages, which sets up Passenger and a default rails app at /var/www/railsapp. This is working fine again after I upgraded Passenger to 2.2.15. I've gone through the Passenger/rails docs and set up my basic rails app with the following in apache2.conf

<VirtualHost *:80>
    ServerName localhost
    DocumentRoot /webapps/blog/public
    <Directory /webapps/blog/public>
        AllowOverride all
        Options -MultiViews
    </Directory>
</VirtualHost>

I'm still logging in as root (this is just a local dev box), so I also tried /root/webapps/blog/public for the DocumentRoot but that didn't work either. I'm a newb at unix, but have a little experience with rails.

Basically, it looks like it's still using the default rails app at /var/www/railsapp.

There's another question here with a link to a lengthy setup guide for Ubuntu/Passenger/Rails which I've looked through and seen some different settings, so I don't know if that guide is dated or what.