You can't extract saves out of ROMs. But if you managed to extract your own demo games and what not, and played it on an emulator, you can extract the save from the RAM.
I'm not sure if there's any specific guides online, but you'll need to identify the area of the RAM to extract and it'll *almost* function as a save (If I'm not mistaken, there's one more edit to achieve but I don't remember where to change)
In any case, if you were just interested in the Pokemon, can use this: