What happens when I trade away my Rotom formes?
In Pokemon Platinum and HeartGold/SoulSilver, there are rooms where Rotom can possess household appliances to gain alternate formes. The appliance is removed from the room while Rotom is in that forme.
When I trade the Rotom away, does my Rotom's Room get its appliance back? Does this differ between versions of the game?
Yes. Rotom automatically reverts to its original form when traded.
Rotom's appliance forms are only available in Platinum, HG/SS, and B/W.