I did some looking around and all the fonts are present on the system. I made a quick test app to compare the fonts on the G2 and Galaxy Nexus and set to figure out how to fix it.
It's pretty simple, just copy the system_fonts.xml file in the zip to \system\etc. You'll probably want to backup and/or rename the existing file first and give it the same file permissions. You'll need root and a file explorer that can mount system. Reboot and you should be able to see the changes.
I copied the file over to internal storage and used Total Commander to copy the xml file after renaming the original file.
The weight is still wrong but at least if the developer wanted to use Roboto and italics, you'll now be able to see italics.