Roboto Flex is a variable font project that upgrades Google's Roboto typeface to provide expanded typographic control through multiple registered axes including weight, width, optical size, slant, and gradient. Commissioned by Google but not officially supported by them, the project leverages OpenType variable font technology to enable parametric typography and reduce file sizes while maintaining the versatility of the original Roboto family, which has become the most popular typeface in the Google Fonts library. The project is developed by Font Bureau and includes source files in UFO format, build scripts using fontmake, and extensive documentation including animation demonstrations and print proofs. It is available under the SIL Open Font License v1.1, with scripts and documentation under Apache 2.0.