Google describes the font as "modern, yet approachable" and "emotional".  Roboto is a free typeface, licensed under the Apache license and was officially made available for free download on January 12, 2012, on the newly launched website. It belongs to the neo-grotesque genre of sans-serif typefaces, and includes Thin, Light, Regular, Medium, Bold and Black weights with matching oblique styles. It also includes condensed styles in Light, Regular and Bold, also with matching oblique designs.
Roboto supports Latin , Greek (partial) and Cyrillic scripts. On Android, the Noto font is used for languages not covered by Roboto, including Chinese (simplified and traditional), Japanese , Korean , Thai and Hindi . 
The font was designed entirely in-house at Google by Christian Robertson, an interface designer for Google, who previously had released an expanded Ubuntu-Title font through his personal type foundry Betatype.  It was released for the first time in 2011 with Android 4.0 "Ice Cream Sandwich" .  Compared to Android's previous system font, the humanist sans-serif Droid , it adopts a more stark grotesque design with oblique styles rather than true italics, and a wider range of weights.
On June 25, 2014, Matias Duarte announced at Google I/O that the typeface for Roboto was significantly redesigned for Android 5.0 "Lollipop" . The most significant changes are seen in the glyphs are: B (shrinking), R, P, a (expanding space), D, O, C, Q, e, g (curving), k, and numbers: 1, 5, 6, 7, and 9. Punctuation marks and the tittles in the lowercase i and j have been changed from a square dot to a rounded dot.
Roboto received variable reviews on its release. Joshua Topolsky , Editor-In-Chief of technology news and media network The Verge , describes the font as "clean and modern, but not overly futuristic – not a science fiction font". However, typography commentator Stephen Coles of typographica.org called the initial release of Roboto “a Four-headed Frankenfont”, describing it as a “hodgepodge” of different typographic styles which do not work well together.  Other type design professionals called out obvious errors in accented glyphs, while John Gruber called the font a " Helvetica ripoff". 
Besides being the default font on the Android operating system, since 2013 it is also the default font of other Google services such as Google+ , Google Play , YouTube , Google Maps ,  and mobile Google Search .
Roboto Bold is the default font in Unreal Engine 4 .
It is also used by Dell as its website's typeface, but Museo Sans is actually the company's corporate typeface. On May 2017, it was reverted back.
Roboto Slab is a slab serif font based on Roboto. It was introduced in March 2013, as the default font in Google's note-taking service Google Keep .  It is available in four weights: thin, light, regular and bold. However, no oblique versions were released for it.