Where can you find rotom in Pokemon Omega Ruby?

In Pokémon Omega Ruby, you can find Rotom in the Old Chateau, which is located in the Route 104 area. To encounter Rotom, you need to enter the building and interact with the television on the second floor, where it will appear. Make sure to be prepared for battle, as it will be at level 15. Additionally, you can also find Rotom in the Secret Base if you have the appropriate decorations.