There are TWO approaches that you can take to use licensed web-fonts on your pages:
1. Font Hosting Services like Typekit, Fonts.com, Fontdeck, etc.
These services provide an easy interface for designers to manage fonts purchased, and generate a link to a dynamic CSS or JavaScript file that serves up the font. Google even provides this service for free (here is an example for the Roboto font you requested).
JS font loaders like the one used by Google and Typekit (i.e. WebFont loader) provide CSS classes and callbacks to help manage the FOUT that may occur, or response timeouts when downloading the font.
<head>
<!-- get the required files from 3rd party sources -->
<link href='http://fonts.googleapis.com/css?family=Roboto' rel='stylesheet' type='text/css'>
<!-- use the font -->
<style>
body {
font-family: 'Roboto', sans-serif;
font-size: 48px;
}
</style>
</head>
2. The DIY approach
This involves getting a font licensed for web use, and (optionally) using a tool like FontSquirrel's generator (or some software) to optimize its file size. Then, a cross-browser implementation of the standard @font-face
CSS property is used to enable the font(s).
This approach can provide better load performance since you have a more granular control over the characters to include and hence the file-size.
/* get the required local files */
@font-face {
font-family: 'Roboto';
src: url('roboto.eot'); /* IE9 Compat Modes */
src: url('roboto.eot?#iefix') format('embedded-opentype'), /* IE6-IE8 */
url('roboto.woff') format('woff'), /* Modern Browsers */
url('roboto.ttf') format('truetype'), /* Safari, Android, iOS */
url('roboto.svg#svgFontName') format('svg'); /* Legacy iOS */
}
/* use the font */
body {
font-family: 'Roboto', sans-serif;
font-size: 48px;
}
TLDR;
There are two major approches to embed custom fonts on your website. Using font hosting services along with @font-face declaration gives best output with respect to overall performance, compatibility and availability.
Source: https://www.artzstudio.com/2012/02/web-font-performance-weighing-fontface-options-and-alternatives/
UPDATE
Roboto: Google’s signature font is now open source. You can now manually generate the Roboto fonts using instructions that can be found here.