Show HN: Explore Pokemon Emerald inside your browser

If you don't have a ROM file on hand (Attention, large GIFs):

[0]: https://i.imgur.com/pYI9ipl.gif

[1]: https://i.imgur.com/isgIRLD.gif

[2]: https://i.imgur.com/GMqDYKr.gif

[3]: https://i.imgur.com/HmvBTAV.png

How does a person get a ROM?