Go to rustboro city and go inside the Devon corp in there go upstairs and you will see a bunch of lab guys talk to the ones on the bottom until you find the one who says he has a resurrection machine let him have the fossil leave the corp come back and talk to him again and he will give you the revived Pokemon from the fossil either lileep or anorith.
No, not all fossils can be found in Omega Ruby or Alpha Sapphire however the fossils that can be found would include the Dome Fossil also known as the Kabuto fossil, Plume Fossil which is the Archen fossil and Armor Fossil which is also the Shieldon fossil can be found in Omega Ruby, the Skull Fossil also known as the Cranidos fossil and Cover Fossil (also known as the Tirtouga fossil) can be found in Alpha Sapphire while the Old Amber Fossil which is the Aerodactyl fossil can be found in both Omega Ruby and Alpha Sapphire.
Take your fossil to the Devon Corporation in Rustboro City. On the second floor, the guy on the back row will take it and turn it into a Pokemon for you.
A Pokemon
you get the Sapphire in dotted hole (you use cut to get into dotted hole)
In Pokemon Ruby and Sapphire you will be given a chance to choose EITHER a Claw Fossil OR a Root Fossil in the Hoenn Desert along Rt 111. The fossils can be given to a scientist at the Devon Corporation and he will revive it into a living Pokemon. The Claw Fossil will be revived into an Anorith and the Root Fossil will be revived into a Lileep. There is only one chance to get these fossils, and once one is chosen the other fossil will sink into the sand forever. After that, the only way to get the other Pokemon is by trading or cheating. ^^^^the above information is correct, except for the last bit. You can get the other pokemon in the fossil maniac's house after beating the elite four west of the pokemon center in fallarbor town. He'll say it's not safe to go through the cave, but go anyway. There you can catch ditto and at the end is the fossil which hasn't been retrieved yet. then when you exit you can talk to the fossil maniac's brother and he will give you DIG
root fossil is lileep claw fossil is anorith
You'll get an Anorith. CLAW fossil- anorith root fossil-lileep helix fossil- kabuto
The Root fossil is the Pokemon Lileep and the Claw fossil is anorith =D
dig dig dig
Cradily can only be obtained in Pokemon Sapphire by evoling a Lileep. Lileeps can be obtained by resurrecting a Root Fossil.
If given to the Devon researcher in the Devon corporation the claw fossil can be revived into Anorith.
talk to the fossil man west of fallarbor town
go to fossil manics house and talk to the girl by the tunnel
From the Fossil Maniac's house, which is in route 114.
fallourbaur town in route 114 there is a house
he is in lavaridge town on the top left side of the town
In Sapphire you only can get one of the two fossils found in the desert. If you have a trade buddy you could trade over the fossil Pokemon from Fire Red/Leaf Green and the second one from Ruby/Sapphire. In emerald you get both Hoenn Fossils, but at different points in the game.