
This is the way I understand MS Office's font logic, and this sort of thing and building templates for design agencies is my full-time job...
Fonts are typically organised in groups of four font files. If we assume that the font is called "FontName", we'd have:
- FontName Regular
- FontName Bold
- FontName Italic
- FontNameBoldItalic (i.e. bold AND italic)
Now, if Office finds such a group of four, it displays only the "Regular" font. "Bold" is automatically mapped to the "Bold" button, "Italic" to the "Italic button" and Bold+Italic is applied when both buttons are pressed. This is why the remaining three font files aren't selectable in the Office font dropdown.
And this may be what you are seeing. It sounds like "Roboto Bold" and "Roboto BoldItalic" are mapped to the corresponding buttons. So,,, it's a feature, not a bug, and you haven't done anything wrong.
BY the way - what happens if you don't install "FontName Italic", for instance? Then Office falls back to calculating an italic version of "FontName Regular". It looks Italic, of course, but looks pretty crappy compared to a proper Italic file, designed carefully. Same with Bold.
So this is what will happen with, say your "Roboto Medium" if you don't have a "Roboto Medium Bold" file (which is quite likely, as Roboto Medium is already pretty... erm... fat.
Hope this helps!