In GB 2.3, the fonts folder is located in /system/fonts, how it works is this, for a font face, it copies the fonts to the original droid fonts names at the same time retaining the pre-defined font names in place.
In my rom, I have this, from adb shell,
sh-4.1# cd /system/fonts
sh-4.1# ls -l
-rw-r--r-- root root 4824 2012-06-13 16:49 Clockopia.ttf
-rw-r--r-- root root 86784 2012-06-13 16:49 DroidSans-Bold.ttf
-rw-r--r-- root root 74656 2012-06-13 16:49 DroidSans.ttf
-rw-r--r-- root root 3725920 2012-06-13 16:49 DroidSansFallback.ttf
-rw-r--r-- root root 119380 2012-06-13 16:49 DroidSansMono.ttf
-rw-r--r-- root root 185228 2012-06-13 16:49 DroidSerif-Bold.ttf
-rw-r--r-- root root 190304 2012-06-13 16:49 DroidSerif-BoldItalic.ttf
-rw-r--r-- root root 177560 2012-06-13 16:49 DroidSerif-Italic.ttf
-rw-r--r-- root root 172916 2012-06-13 16:49 DroidSerif-Regular.ttf
Notice how the names are retained but are in fact Roboto fonts! :)
Sounds like the fonts are installed into a different name in which the ROM is not picking it up. For example, suppose the font's name is 'MyFont.ttf' and that gets copied over, but is not copied into 'DroidSans.ttf'... just a guess.
BTW, what Android is that ROM you're referring to?
Edit: It has been ascertained that this is Honeycomb (Android 3.2.1). Do the following:
- Plug in cable to Toshiba Thrive
- From command line, issue this, adb shell ls /system/fonts
- Select all the text of that output, copy to clipboard, and go to http://www.pastebin.com and create a new paste, paste in the contents and it will create a linky for everyone to see, put that linky into the comments below and will look at it :)