Chromium's Font Packager allows you to easily create your own flashable font packs using fonts of your choice. All you need is 4 base styles: Regular, Italic, Bold and Bold Italic. The utility will do the rest of the work for you. This includes duplicating the fonts and renaming them appropriately so that every single Roboto font found in your phone is replaced. thus ensuring that all text gets themed. This app also gives you the option to copy your freshly built font pack to your phone, and reboot the phone into recovery so that you can then flash the zip.
Download - Version 1
Download - Version 1.1
Download - Version 1.2
Version 1 -Initial Release Version 1.1 -Add a few extra touches & polish Version 1.2 -Give user an option to directly push font files into system, rather than having to manually flash the zip via recovery -Make it more efficient/logical