Officially, Roku only lets you download apps that are available on their app store, i.e., the Roku Channel Store. However, there are some workarounds through which you can install and watch IPTV on ...
Install the App: Open the downloaded APK file ... sources and be cautious of any permissions the app requests. For Roku devices, apps must be built using BrightScript and packaged in a ZIP file.
You can also search GitHub for ropm packages, but since GitHub doesn't support searching by keyword, you'll need to know what you're looking for. This provides unique challenges for a Roku package ...