If you are building an app in Android Studio and want to change the font in the app to Roboto or any other Fonts, this tutorial might help you.

How to use Roboto Font in your Android Studio Project | Kodewaala

For changing the font we use a library called Typerlib
For using this library in your Android Studio project then you have to make an entry in your build.gradle file.

dependencies {
compile
'com.elmargomez.typer:typerlib:1.0.0'
}

Click sync now. Android Studio IDE will download the library for you and adds it to your project.
Now you can use that to text boxes, text views, any component having text.

Below are the Example codes.

TextView txtView1 = (TextView) findViewById(R.id.yourTxtView1);
TextView txtView2 = (TextView) findViewById(R.id.yourTxtView2);
TextView txtView3 = (TextView) findViewById(R.id.yourTxtView3);
TextView txtView4 = (TextView) findViewById(R.id.yourTxtView4);

txtView1
.setTypeface(Typer.set(yourContext).getFont(Font.ROBOTO_REGULAR));
txtView2
.setTypeface(Typer.set(yourContext).getFont(Font.ROBOTO_CONDENSED_ITALIC));
txtView3
.setTypeface(Typer.set(yourContext).getFont(Font.ROBOTO_THIN));
txtView4
.setTypeface(Typer.set(yourContext).getFont(Font.ROBOTO_BOLD));

Use Android Studio to view all available Fonts. Autocomplete class Font by clicking " Ctrl + space ".