Dawn Stones are not found in Victory Road in Pokémon Diamond. In fact, they are not found anywhere in the wild in the game.
Here's how you can obtain a Dawn Stone in Pokémon Diamond:
* Trade: The easiest way is to trade with someone who has already found one.
* Breeding: You can breed a Pokémon holding a Dawn Stone with another Pokémon to pass the held item to an offspring. This is a more difficult method as finding a Pokémon holding a Dawn Stone is the initial challenge.
Note: The Dawn Stone is used to evolve a Snorunt into a Froslass.