Budew might not look like the toughest Pokemon in Brilliant Diamond and Shining Pearl, but its final form is one of the strongest Grass-types around in Roserade.
Pokemon Brilliant Diamond and Shining Pearl trainers will probably come across the Grass-type Budew many times in the early areas of the Sinnoh region
Once trainers have caught a Budew, they can put it on the path to greatness. It needs to level up with high Friendship into Roselia, which will then evolve into Roserade when exposed to a Shiny Stone.
Evolving Budew to Roselia in Pokemon Brilliant Diamond and Shining Pearl
Budew needs to have a high Friendship level in order to evolve into Roselia. On top of that, it needs to level up during the daytime for that evolution to take place in Pokemon Brilliant Diamond and Shining Pearl.
You can use the Friendship Checker app on your Poketch at any time to see the progress you have made. Do this after plenty of walking and battling with Budew, and maybe even getting Budew a massage in Veilstone City.
After the Friendship level in the app shows two hearts appearing near Budew when you interact with it, level it up during the day with a Rare Candy or by gaining EXP to obtain a Roselia.
Evolving Roselia into Roserade in Pokemon Brilliant Diamond and Shining Pearl
Once you have a Roselia in your Pokemon collection, you can use a Shiny Stone to evolve it into the mega powerful Roserade. Shiny Stones may not be that easy to come by, however.
Iron Island and Route 228 both have a Shiny Stone on the ground as a Poke Ball pickup. Others can be found while having a Pokemon with the Pickup Ability in your party.
They will randomly pickup held items after a battle, and there is a chance it could be a Shiny Stone. You can also get one as a reward at the Battle Tower. When you do, go to your Bag and use it on Roselia to evolve it into Roserade.