android:fontFamily="sans-serif"// roboto regular

android:fontFamily="sans-serif-light"// roboto light

android:fontFamily="sans-serif-condensed"// roboto condensed

android:fontFamily="sans-serif-black"// roboto black

android:fontFamily="sans-serif-thin"// roboto thin (android 4.2)

android:fontFamily="sans-serif-medium"// roboto medium (android 5.0)