Hi,

Thanks for working on this patch.

Note that I'm not a Guix maintainer (I only managed to send some patches
and get them accepted), but I've seen several things to fix in this
patch and I've also some questions:
- You used 'license:asl2.0' as the license, while looking rapidly at
  the source I didn't find any license. Do you know where the license
  is stated in the font source code?
- If you really want to fix font-adobe-source-code-pro and font-dseg
  code style, it should be done in one or two separate patches. Two
  patches are probably easier for maintainers to review.
- I've also noticed that this patch lacks any commit message details.
  Something like that should work:
    gnu: Add font-google-roboto-mono
    
    * gnu/packages/fonts.scm (font-google-roboto-mono): New variable.

Also there may or may not be additional issues as I've only looked at
it rapidly.

Denis.