Thanks for your help.
I changed the font successfully by modifying the file userstyle.css +download the font and use exact path:
body
{
font-family: Roboto;
font-style: normal;
font-weight: 400;
}
/* roboto-regular - latin */
@font-face {
font-family: 'Roboto';
font-style: normal;
font-weight: 400;
src: url('fonts/roboto-v19-latin-regular.eot'); /* IE9 Compat Modes */
src: local('Roboto'), local('Roboto-Regular'),
url('fonts/roboto-v19-latin-regular.eot?#iefix') format('embedded-opentype'), /* IE6-IE8 */
url('fonts/roboto-v19-latin-regular.woff2') format('woff2'), /* Super Modern Browsers */
url('fonts/roboto-v19-latin-regular.woff') format('woff'), /* Modern Browsers */
url('fonts/roboto-v19-latin-regular.ttf') format('truetype'), /* Safari, Android, iOS */
url('fonts/roboto-v19-latin-regular.svg#Roboto') format('svg'); /* Legacy iOS */
}
But when I modify something in FontFacePlugin and save the configuration, it makes something wrong and can not load the page. I have to reserve to the last version.