So don't get a Roku then

I was just offering a suggestion since it sounds like you already paid for
Disney+, if you were really looking for a way to watch on a regular TV over the next three years. The likelihood is that Disney and
Amazon will work it out and it will be moot anyway.
ETA: Besides, if Amazon and Disney
don't work it out, then the Fire Stick and Roku don't do the same thing--one would play Disney+ and one wouldn't.