Unfortunately you can't. Roselia can't be caught in the wild in Emerald. With that being said, it may be possible in a copy of Ruby or Sapphire, and you could trade it over. Otherwise, you're pretty much sunk.
you trade from ruby/ sapphire/ or XD gale of darkness
Rosealia was created in 1993.
give it a shiny stone and it will evolve into roserade.
i think rosealia golduck crobat electrabuzz Rhiperior and beedrull
You can't find a Dawnstone in Pokemon Emerald
go to the safari zone in emerald
he is the champion in emerald
You cant find one in emerald BUT... you can trade from FireRed/LeafGreen
You cannot find one in emerald (unless you trade or hack)
Sorry, you can't get Mantine in emerald
You can´t find it on Emerald
you can't get paras in emerald