I figured out how to catch Rotom :D I needed the national dex first duh of course *dumb* XD;; And yes, I have the national dex now. Uh.. >> << I manipulated the time on my DS to get Fuwante. XD;
Go to Hakutai Forest, at night. It needs to be at night, even though you can see the ghosts during the day, Rotom won't appear after you've seen them.
After entering the creepy house, click A on the statue in front of you (I don't know if it works without clicking the statue, I haven't tested yet). Go straight up into the dining room of the house. Most likely, the first spirit won't be there yet, so keep leaving and entering the room again till you see an old man. Once he floats off the screen, you'll be able to move again.
Leave the dining room, and head up the steps, then go in the north door. In this room there are five doors. Go into the one just right of the far east door. Keep doing what you did in the dining room until a little girl appears in the room just right of the one you're in. (Again I don't if this'll work if you go into the far east room. Although if it does, you're gonna have a creepy little girl walk straight through you D:)
The little girl floats off through the door. Now leave the room and go two doors left. Click on the TV, click on yes when the prompt asks you, and Rotom will appear.
Its only level 15 though, which very much surprised me, so you need to take a pretty weak Poke with you to battle. Also it has Darkrai's music which was pleasent. I love and desperately want an .mp3 of that song.
[Off Topic] Woo that was weird O_o the last few days, my firefox browser wouldn't let me cut/copy/paste. Now its back to normal. o_O [/Off Topic]