No, trading pokemon from there to newer games is the only way. Roserade is a newer pokemon emerald is an older game.
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from trade
Roserade can only learn extrasensory through breeding. If you have a Pokemon that already knows that move, try to breed it with Roserade.
Pokemon Ruby has Pokemon that Pokemon Sapphire does not and Pokemon Sapphire has Pokemon that Pokemon Ruby does not.
Shiny Stone
You can trade from Pokemon Ruby to another Pokemon Ruby using a link cable.