The VISIONary app is so-named because of the other moniker for the G2, 'HTC Vision'. The app is available free from the Android Market, but donation is encouraged. Don't you want MoDaCo to continue such useful development? After downloading the app to your G2, you simply select the icon, and you're done.
Just a note: you need to have your USB debugging enabled. To do so, go to Settings>Applications>Development, and check the 'USB Debugging' box. When VISIONary completes the rooting, it will open /data/local/visionary.sh. If you have things you want to load with your root, you can place them in this file. And there you go! Enjoy your rooted device, and the satisfaction of having circumvented HTC's sneaky software.
source: XDA-Developers via IntoMobile