Where do you get rocksmash in Pokemon ruby?

You can't get "Rocksmash" in Pokemon Ruby. That move was introduced in Pokemon Diamond and Pearl.

In Pokemon Ruby, the move you're likely thinking of is Rock Smash.

Here's how to get Rock Smash in Pokemon Ruby:

1. Beat the Elite Four: You'll need to complete the main story of the game and defeat the Elite Four.

2. Talk to Professor Birch: After defeating the Elite Four, talk to Professor Birch in his lab in Littleroot Town.

3. Receive the HM: He'll give you HM06, which contains the Rock Smash move.

4. Teach it to your Pokemon: You'll need to visit a Move Tutor to teach Rock Smash to one of your Pokemon.

Rock Smash is useful for breaking rocks in the world, revealing hidden items or paths.