I checked the PokemonDB pages for Starly, Staravia, and Staraptor, but none of them can be found in OR / AS.
Sorry, but the only way you're going to get a Staraptor or its evolutionary line is by trading.
You could (but this works only if you or a friend has an X / Y game) catch a Starly and / or a Staravia on Route 11: Miroir Way. Afterwards, you can trade it over to your Omega Ruby / Alpha Sapphire game.
The same applies to older games, but you would have to transfer it over, which isn't really worth the hassle.
Hope I helped!
Sources: PokemonDB - Starly, PokemonDB - Staravia, Pokemon DB - Staraptor, Experience