The aptly named Roboto Serif was designed in collaboration with Greg Gazdowicz of CommercialType to create a more readable companion to the Roboto Sans typeface.
The old Roboto letters were redrawn from scratch to create a new and original design. It is possible to mix the sans-serif and serif versions in a single design with the same vertical proportions of Roboto Sans.
It's possible that chunkier, retro-styled serif typefaces are coming back in style in a big way after years of minimalist san-serif designs dominating. Thanks to the more distinct letter shapes, Serif fonts are considered to be easier to read, and this is due to the fact that the variable fonts that can automatically change and adjust the letterforms for different size displays, expands on by virtue of being a variable type that can change and adjust the
For over a decade, Roboto has been used in one form or another by the company; it was first introduced alongside Ice Cream Sandwich as the default for the company's mobile OS. Over the years, Roboto has seen plenty of variations, but it has been superseded as the company's primary fonts by Product Sans.
It's entirely possible that one day the new, friendly looking Roboto family of open-source fonts will be used by the company.