Roku is only sold and supported in 17 regions. You did not say where you were located, but if not one of these 17 regions, then you are not in a supported region.
That's it. Roku device cannot be purchased through official channels anywhere else.
As for app availability, Roku leaves that up to the developer. Netflix, for instance, is available in all areas. That's because Netflix decided to support a Roku app there. If Disney+ is not, that's because Disney decided to not support a Roku app there. If Disney makes it available, it will appear in the Channel Store there, but it's Disney's decision, not Roku's.
By the way, you'll find most services do like Disney, not like Netflix. Most will not support an app where the device itself is not supported.
DBDukes Roku Community Streaming Expert Note: I am not a Roku employee.
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