On the route west from mauville city look for Roselia in the grass it's rare to find though.
Route 117
you cant catch roselia in emerald, but I'm pretty sure you can catch it in Sapphire, so just trade it over
machop,poocheyana,magicarp,garados,roselia,pikachu,
Try the grass on Route 117 outside of Mauville City. Roselia has about a 30% catch rate there.
I don't think Roselia evolves in Pokemon Sapphire, but i do know that it evolves in Pokemon Diamond and Pearl. If I'm wrong please do tell ASAP. Thank You.
It is obtainable in RUBY AND SAPPHIRE but not EMERALD. You can find it on Route 117. You may need to use a level 10+ Pokemon to weaken it.
Catch a Roselia and evolve it
you have to trade it from diamond to soul silver and you can't actually catch Roselia wild in Pokemon soul silver.
How do you catch latios in Pokemon sapphire
There are many Pokemon you catch that are similar in sapphire and emerald but there are many Pokemon emerald can only get and not sapphire.
You can't catch a ditto in Pokemon Sapphire, but you can trade it from Pokemon Emerald/FireRed/LeafGreen.
In every single Pokemon game and version, there are different Pokemon you can capture and train. In some games, you can catch one species of Pokemon, but not be able to catch it in another. In this case, surskit cannot be caught in emerald version, same with Roselia, while in sapphire and ruby, those Pokemon can be caught.