How to include Roboto font in webpack build for Material UI?

For a progressive web app based on Material UI (React) and built with Webpack, how do I properly include Roboto font(s) so that the app does not depend on Google servers and fonts also work offline ?

The installation page just references the Google fonts page, but that obviously forces fonts to be downloaded from Google servers.
A similar Material UI Issue exists regarding Roboto font, but still relies on Google providing the font files.
I found a NPM package providing the Roboto font files, but I'm not sure how to include those files as lots of styles and font formats are provided and I don't know what styles Material UI really needs. Also, importing those font families simply via @import seems to have performance issues.

So, what is a good and simple solution to bundle the right Roboto files with my application?

Solution

This is how my team went about including the Roboto fonts in our Webpack project:

Download the Roboto fonts and make a CSS file in a font-specific folder

Create a folder (/fonts).
Download all of the Roboto fonts from Font Squirrel. Go to the Webfont Kit tab, then press the Download @font-face Kit button with default settings.
Move the fonts into /fonts.
Create the CSS file (/fonts/index.css). We got the contents for this file from this tutorial.

index.css:

* {
  font-family: Roboto, sans-serif;  
}

@font-face {
    font-family: 'Roboto';
    src: url('Roboto-Regular-webfont.eot');
    src: url('Roboto-Regular-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-Regular-webfont.woff') format('woff'),
         url('Roboto-Regular-webfont.ttf') format('truetype'),
         url('Roboto-Regular-webfont.svg#RobotoRegular') format('svg');
    font-weight: normal;
    font-style: normal;
}
 
@font-face {
    font-family: 'Roboto';
    src: url('Roboto-Italic-webfont.eot');
    src: url('Roboto-Italic-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-Italic-webfont.woff') format('woff'),
         url('Roboto-Italic-webfont.ttf') format('truetype'),
         url('Roboto-Italic-webfont.svg#RobotoItalic') format('svg');
    font-weight: normal;
    font-style: italic;
}
 
@font-face {
    font-family: 'Roboto';
    src: url('Roboto-Bold-webfont.eot');
    src: url('Roboto-Bold-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-Bold-webfont.woff') format('woff'),
         url('Roboto-Bold-webfont.ttf') format('truetype'),
         url('Roboto-Bold-webfont.svg#RobotoBold') format('svg');
    font-weight: bold;
    font-style: normal;
}
 
@font-face {
    font-family: 'Roboto';
    src: url('Roboto-BoldItalic-webfont.eot');
    src: url('Roboto-BoldItalic-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-BoldItalic-webfont.woff') format('woff'),
         url('Roboto-BoldItalic-webfont.ttf') format('truetype'),
         url('Roboto-BoldItalic-webfont.svg#RobotoBoldItalic') format('svg');
    font-weight: bold;
    font-style: italic;
}
 
@font-face {
    font-family: 'Roboto';
    src: url('Roboto-Thin-webfont.eot');
    src: url('Roboto-Thin-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-Thin-webfont.woff') format('woff'),
         url('Roboto-Thin-webfont.ttf') format('truetype'),
         url('Roboto-Thin-webfont.svg#RobotoThin') format('svg');
    font-weight: 200;
    font-style: normal;
}
 
@font-face {
    font-family: 'Roboto';
    src: url('Roboto-ThinItalic-webfont.eot');
    src: url('Roboto-ThinItalic-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-ThinItalic-webfont.woff') format('woff'),
         url('Roboto-ThinItalic-webfont.ttf') format('truetype'),
         url('Roboto-ThinItalic-webfont.svg#RobotoThinItalic') format('svg'); (under the Apache Software License). 
    font-weight: 200;
    font-style: italic;
}
 
@font-face {
    font-family: 'Roboto';
    src: url('Roboto-Light-webfont.eot');
    src: url('Roboto-Light-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-Light-webfont.woff') format('woff'),
         url('Roboto-Light-webfont.ttf') format('truetype'),
         url('Roboto-Light-webfont.svg#RobotoLight') format('svg');
    font-weight: 100;
    font-style: normal;
}
 
@font-face {
    font-family: 'Roboto';
    src: url('Roboto-LightItalic-webfont.eot');
    src: url('Roboto-LightItalic-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-LightItalic-webfont.woff') format('woff'),
         url('Roboto-LightItalic-webfont.ttf') format('truetype'),
         url('Roboto-LightItalic-webfont.svg#RobotoLightItalic') format('svg');
    font-weight: 100;
    font-style: italic;
}
 
@font-face {
    font-family: 'Roboto';
    src: url('Roboto-Medium-webfont.eot');
    src: url('Roboto-Medium-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-Medium-webfont.woff') format('woff'),
         url('Roboto-Medium-webfont.ttf') format('truetype'),
         url('Roboto-Medium-webfont.svg#RobotoMedium') format('svg');
    font-weight: 300;
    font-style: normal;
}
 
@font-face {
    font-family: 'Roboto';
    src: url('Roboto-MediumItalic-webfont.eot');
    src: url('Roboto-MediumItalic-webfont.eot?#iefix') format('embedded-opentype'),
         url('Roboto-MediumItalic-webfont.woff') format('woff'),
         url('Roboto-MediumItalic-webfont.ttf') format('truetype'),
         url('Roboto-MediumItalic-webfont.svg#RobotoMediumItalic') format('svg');
    font-weight: 300;
    font-style: italic;
}

Use the file-loader webpack module to load in the font files so webpack can recognize them

npm install --save file-loader (https://www.npmjs.com/package/file-loader)
In your webpack config, use the loader like so:

webpack.conf.js:

loaders: [
  ..., {
    test: /\.(woff|woff2|eot|ttf|svg)$/,
    loader: 'file-loader',
    options: { name: '[name].[ext]', outputPath: 'fonts/', }
  },
  ...
]

Import the font css file in the main entry of the app

App.js:

import './fonts/index.css';

And that's it. Your application's default font should now be Roboto.

EDIT: Which Roboto Fonts does Material-UI actually use?

Part of this question is determining the right Roboto fonts to include in the project since the entirety of the Roboto fonts is almost 5MB.

In the README, the instructions for including Roboto point to: fonts.google.com/?selection.family=Roboto:300,400,500. Here, 300 = Roboto-Light, 400 = Roboto-Regular, and 500 = Roboto-Medium. These correspond to the font weights defined in the typography.js file. While these three font weights account for usage in almost the entirety of the library, there is one reference to Regular-Bold in DateDisplay.js. If you are not using the DatePicker, you should probably be safe to omit that. Italics font styling is not used anywhere in the project aside from the GitHub markdown styling.

This information is accurate at the time of this writing, but it may change in the future.