From Bulbapedia, the community-driven Pokémon encyclopedia.
The bedroom is the room that the player resides in in his or her own house. It is where the player first starts the game and where the player ends up after beating the Pokémon League. Most versions of the bedroom are included with a PC and a bed, and often the current Nintendo console. Also in most games, there is a Potion stored in the PC.
In Pokémon Red, Blue and Yellow
In Generation I, Red's bedroom has a PC, a bed, and a TV with an SNES hooked up to it. It serves no other purpose, although the PC can be used to access the player's item storage.
In Pokémon Gold, Silver, and Crystal
Gold or Kris's bedroom is a bit more fancy than Red's. Unlike Red's, it can also be customized to include several Poké Dolls, as well as beds, game systems, and carpets. The Town Map hanging on the wall can also be replaced with one of several posters of different Pokémon.
The bedroom can be viewed in 3D in Pokémon Stadium 2.
In Pokémon Ruby, Sapphire, and Emerald
Brendan or May's bedroom, which are essentially reflections of each other, feature a toned-down version of the Generation II decoration system, as now players were only able to set Poké Dolls on the mat. Much of the customization, however, was moved into the player's secret base. A clock on the wall in the room was also the only indicator of time in the game. The game system in the room is a Nintendo GameCube with a Game Boy Advance hooked up to it as a controller.
In Pokémon FireRed and LeafGreen
FireRed and LeafGreen featured an enhanced version of the bedroom from Generation I. The only difference is the SNES being replaced with a NES.
In Pokémon XD: Gale of Darkness
While Pokémon XD: Gale of Darkness starts with Michael inside of the Battle Sim instead of his bedroom, there is in fact a bedroom that can be used for healing Pokémon within the building, and it is where Michael ends up after Greevil's defeat.
In Pokémon Diamond and Pearl
Due to the PC no longer having the item storage functionality, Lucas or Dawn's PC only gives hints on how to play the game. The secret bases return from Generation III, however they are now underground. This time around, a Wii is in the bedroom.