Platforms like Mirai GBA and PokeUniverso often host "pre-patched" versions that combine the NDS enhancements with a 100% Spanish translation.
Real-time lighting and time-based events are added, which were absent in the original FireRed. How to Find and Play the ROM in Spanish
For players specifically looking for the "Español" version, there are several dedicated community resources: pokemon rojo fuego nds with rom espanol new
The latest "new" versions of Pokémon Rojo Fuego for NDS offer a dramatic upgrade over the 2004 GBA release:
Disfruta de Pokémon Edición Rojo Fuego y ... - Pokemon.com Platforms like Mirai GBA and PokeUniverso often host
Many of these ROM hacks include Pokémon from generations 1 through 4 (up to 493 Pokémon), and some even include newer types like the Fairy type.
The dual-screen layout of the NDS is fully utilized for menus, battle commands, and the Pokédex. - Pokemon
To play these fan-made NDS versions, you will typically need an NDS emulator such as SuperNDS for Android or a flashcart (like an R4) if playing on original hardware. Most ROMs come in .nds format and range in size depending on the amount of new content added.