To get a rotom you're gonna need a ditto to trade. First you have to fly to white forest with a ditto in your party and head towards route 15 and past the poke transfer lab and enter the RV to the east of the lab. There will be a girl scientist wanting to trade her rotom for your ditto and there you go.I traded my lv. 65 Ditto and got rotom at lv. 60 nicknamed Eeks. Rotms moves included substitute, Electro ball, Hex, and Charge. His OT should be Lillian, plus he has a max elixir as a hold item, an added Bonus! His stats were...

Attack: 77

Defense: 98

Sp. Atk: 131

Sp. Def: 127

Speed: 126

Also if you change want to change his form go the Mall at route 9 and to the left should be a doorway. In there will be an item, an old man, an a bunch of cardboard boxes. Interact with the boxes and rotms form will change based on which box you selected. You can find a ditto in the Giant Chasm year round. Hope I Helped!!!