it's easy
every folder of those you downloaded has a different kind of roboto font, means they are different fonts
example: "roboto_regular_macroman"
to use any of them:
1- extract the folder of the font you want to use
2- upload it near the css file
3- now include it in the css file
example for including the font which called "roboto_regular_macroman":
@font-face {
font-family: 'Roboto';
src: url('roboto_regular_macroman/Roboto-Regular-webfont.eot');
src: url('roboto_regular_macroman/Roboto-Regular-webfont.eot?#iefix') format('embedded-opentype'),
url('roboto_regular_macroman/Roboto-Regular-webfont.woff') format('woff'),
url('roboto_regular_macroman/Roboto-Regular-webfont.ttf') format('truetype'),
url('roboto_regular_macroman/Roboto-Regular-webfont.svg#RobotoRegular') format('svg');
font-weight: normal;
font-style: normal;
}
watch for the path of the files, here i uploaded the folder called "roboto_regular_macroman" in the same folder where the css is
then you can now simply use the font by typing font-family: 'Roboto';