Get FontNames in Xamarin iOS source : https://dev.to/codingcoach/using-font-awesome-in-xamarinforms--3mh

AppDelegate.cs

 // The UIApplicationDelegate for the application. This class is responsible for launching the 
    // User Interface of the application, as well as listening (and optionally responding) to 
    // application events from iOS.
    [Register("AppDelegate")]
    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
    {
        //
        // This method is invoked when the application has loaded and is ready to run. In this 
        // method you should instantiate the window, load the UI into it and then make the window
        // visible.
        //
        // You have 17 seconds to return from this method, or iOS will terminate your application.
        //
        public override bool FinishedLaunching(UIApplication app, NSDictionary options)
        {
            global::Xamarin.Forms.Forms.Init();
            global::Xamarin.Forms.FormsMaterial.Init();

            foreach(var familyNames in UIFont.FamilyNames.Where(f=>f.StartsWith("Roboto")).OrderBy(x=>x).ToList())
            {
                Console.WriteLine("*" + familyNames);
                foreach(var familyName in UIFont.FontNamesForFamilyName(familyNames).OrderBy(c=>c).ToList())
                {
                    Console.WriteLine("*" + familyName);
                }
            }
            LoadApplication(new App());

            return base.FinishedLaunching(app, options);
        }
    }