This is basically the same problem as Bug 464666. It was temporarily fixed in media-fonts/roboto-20130731, but has returned in 1.2. It appears, from looking at the files installed by the 1.2 ebuild, and by the contents of the Roboto-1.2 zip, that Google's upstream copies of the Black fonts have reverted to their previous problem: they're mistakenly marked as having Book weight, not Black (this can be confirmed with fontforge, the OS/2 weight class). This makes fontconfig assume they're a reasonable choice when selecting a normal-weight Roboto font. The previous fix to the Medium-weight problem still seems to be effective, it's just that Google has re-broken the Black weights again. Reproducible: Always
I should note that I have a quite old issue filed against Android about this Black weight problem, but as that's a huge active tracker and this issue doesn't fit exactly squarely as an Android problem, it's never gotten any activity. That bug is at https://code.google.com/p/android/issues/detail?id=36981 Separately, I reported to the Fontconfig mailing list the issue with the Medium weight, which was coming from a fontconfig issue and not a problem with the fonts themselves (this is the one that was fixed by the 90-roboto-regular.conf file). Fontconfig actually merged a change altering the default weight from Medium to Normal, though I'm not sure when that will make its way into a release: http://lists.freedesktop.org/archives/fontconfig/2013-October/004978.html
I consider this the same bug, so let's continue in bug #464666 *** This bug has been marked as a duplicate of bug 464666 ***
