Answer 1

What Pokemaster told of is right for HG/SS
If you're refering to diamand/pearl/platinum, it's on your way to Snowpoint City. There is a house on route 17. Inside, a man says he lost a hm outside. If you use your dowsing app, you can find it. It's rock climb. You need to beat the Snowpoint Gym leader Candice to use it out of battle. If you go back in and talk to him, he'll also give you an icical plate. Double win. :)

Answer 2

You get Rock Slide (TM80) after beating Pewter City Gym (in Kanto, after beating the Elite 4).

You get Rock Climb (HM08) from Professor Oak after defeating all 16 gyms.
By the way, Rock Climb is not a rock-type move, it is a normal move for some reason.

Comments

Do you know how to get them in platinum?

Answer 3

In diamond/pearl/platinum tm80 rock slide is found in mt.coronet in the middle of floor2.