@coachwkm
The only channels/apps that can be downloaded/installed on a Roku device are available in the Roku Channel Store. https://channelstore.roku.com/browse
As you can see in its description, "Downloader is an app that helps you easily download files onto your Fire TV, Google TV, Android TV, Android Phone, Android Tablet, or Fire Tablet." https://www.aftvnews.com/downloader/
As such, Downloader is not available for install on a Roku device/RokuTV.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, 4802, 4850, Premiere+ 3921, Express 4k+ 3941, Streambar 9102