When you beat the elite 4 go on the route where this tuber and his sister go behind them and there should be raquaza he will be at level 70
You catch them. Or trade for them.
groudor,rayquazza and more
tropius is a rare pokemon. but you can catch him near the water institute.
Mt. Pyre, but they are rare, be patient
Rare Pokemon come randomly when you're in the grass or cave.
If by rare you mean "Legendary" or "Ancient" Pokémon then you wont be able to catch any until you've obtained 7 Badges, once you have, you can catch Groudon since you have Ruby Version, if you have anymore questions about other rare Pokémon; Let me know! Hope I've helped. -Jolty94.
Yes you can, its rare though. Go to the Petalburg Woods.
you can catch ralts on route 102 on emerald sapphire and ruby, but they are rare
he is in th routs 124and126 but is a very rare Pokemon to catch
Yes! It is found at the Safari Zone. Though it is slightly rare!
Shroomish is a rare Pokemon in Ruby and Saphire but you can find it in the Petalburg woods.
you catch it in the dessert north of Mauville in Ruby, Saphire and Emerald.If you want it in Pokemon Diamond and Pearl then you can catch it in Route 228. It is really rare. It is not catchable in Platinum.