Unfortunately, The Mandalorian isn't on Netflix or Amazon Prime Video. The show is only available on Disney+. Since Disney+ has a streaming channel on Roku, it is possible to watch The Mandalorian on Roku. However, Disney+ is only licensed to show its content to certain countries in the world due to licensing and distribution reasons. While a VPN can hypothetically let you watch the show in a country where Disney+ isn’t available, doing this goes against the platform’s T&Cs and could be considered copyright infringement.