go to the desert, go way down to the bottom of the desert, go in the cave, go straight up to the writing press "a" then go right twice and go down twice, then use strenght and the door will open.
In Diamond you can't catch Regirock, you have to migrate it from Pokemon Ruby, Sapphire, or Emerald.
u have to migrate them from ruby Sapphire emerald
how do i get regirock
You can only get a regice, regirock, and a registeel by migrating them from ruby or Sapphire. If you migrtate these Pokemon you can also catch regigigas.
to get regirock in Pokemon platinum, you have to upload it from ruby, Sapphire, or emerald.
you can ethier catch them or use acheat when you get so far in the game. you catch them. they are kyogre,deoxys,castform,regirock,registeel,and regiice.
u can get kyogre,rayquaza,latios,latias,regirock,regice,registeel. that is all i Know.
Kyogre, Regice, Registeel, and Regirock.
Regice,Regirock,Registeel,and Kyogre
some secret Pokemon aren't real like Freeza or Deserta thats just regirock and regice you can catch them by watching on youtube MunchingOranges' pokemon sapphire walkthrough but first you MUST POST HALL OF FAME :)
there are a few legendary Pokemon in sapphire; the Pokemon are Kyogre, Rayquaza, Latios, Regirock,Registeel, Regice, and Deoxys
i don't think you can