It's different in different versions.
I don't think you can get regirock in pokemon ruby.
I think it has something to do with braille. And the move dig. If I'm not correct, look it up on youtube.
thre is no regifire only regirock.you can see regirock cave on the desert go down on the desert and you will see a cave go in there. if you see the dotted letters use strength and a hole will open go in there and you will see regirock,remember this will work after you beat the elite four.
Regirock is at the bitten if the desert on route 111. You need to have already opened the outside door by going to the cave after pacifidlog town. Take a relincanth and a wailord. Put the relincanth first and the wailord last in your party. Go in, using dig, then go to the back room and talk to the center of the wall that has Braille. Go to regirocks cave when it is open, then go in. Walk to the Braille at the top of the cave. Read it, then take two steps left and two steps down. Then use rock smash. If you do exactly that, a door will open where the Braille was. Walk in and regirock will be there.
in mystery duguen or Pokemon games?
in aegis cave in the rock chamber{ice will be first so you will fight regiice then regirock}
You go into a underwater place where theres braille then have a wailord at the top of you party and a relecanth athe bottom then hey presto you have opened all the caves.
Read the braille then do the following: Step right twice then step down twice then use rock smash the door should open.
In Pokemon mystery dungeons explorers of sky the regis are in watchman cave
Get Regigegas from the giveaway and go into the cave on route 224
It's really simple: You just go in the middle of the cave.
You must has a pokemon had a Rock Smash.You go to Desert Ruins and go to a cave does open when you go to Pacificlog and go to a some earthquake and go again there the cave is open,Go enter, Read the text Go down 2 and go right 2 ,...