Android 5.0 seems to have trouble rendering custom fonts. This issue does not occur pre Android 5.0 and it does not occur in Android 5.1 (API 22). Here is an example using
Google has acknowledged that this was an issue in Android 5.0, and has fixed it in Android 5.1: https://code.google.com/p/android-developer-preview/issues/detail?id=608&thanks=608&ts=1404735239
As for getting custom fonts to work on Android 5.0, there is a recommended work around in the issue page that I linked to above. It is post #16 on the issue. You need to convert your TTF font file to TTX and then convert it from TTX to TTF. You can use this tool to do so: https://github.com/behdad/fonttools/
I found these guides to be helpful for setting up fonttools:
Windows: http://glyphrstudio.com/ttx/
OSX:http://www.fontgeek.net/blog/?p=435
After installed, in terminal or the command prompt navigate to the directory where your TTF file is and run the command:
ttx font_file.ttf
Where "font_file" is the name of your, well, font file. This will output a font_file.ttx file in the directory you are currently in. Then, on this new font_file.ttx file, simply run the command:
ttx font_file.ttx
This will output a new TTF file of your font, and you can use this one in your Android project. These steps worked for me.