He's not in the game at all the professor in that game is birch.
If you're talking about Professor Oak, he's not in Pokemon Sapphire.
there is no professor oak in ruby and sapphire
professor oak only appears in diamond but if you want to meet him try sapphire version
At the beginning of the game, Professor Oak is in Mr. Pokemon's house. Mr. Pokemon's house is north of Cherrygrove City. After that, Professor Oak is in Pallet Town in his Pokemon lab.
Obtaining all of Professor Oak's Pokemon can only be accomplished via Cheat Codes.
Prof. Rowan isn't in Sapphire.
from the Pokemon professor at the beginning of the game
you dont
nowhere.
In the Pokemon animated series, Professor Oak has a Rotom. Professor Oak caught his Rotom on Torom Island. Oak's Rotom is prominently featured in the Pokemon XY series.
Pikachu was in the Poke Ball that Ash had received from Professor Oak.
"How do you catch Professor Oak" You can't! He's a person NOT a pokemon. Possibly with the Action Replay