Well i had this problem to and the answer is Route 228/Iron Island HOPE THAT HELPED
=)
When you get a shiny stone... Give him/her a shiny stone
You can find a Shiny Stone in Route 228 in Pokemon Diamond and Pearl. In Pokemon Platinum, you can also find a Shiny Stone on Iron Island.
the shiny stone is used to evolve Togetic and Roselia.
Shiny Stone
You can find a Shiny Stone at Route 228 and also at Iron Island
The Shiny Stone is an evolutionary stone that allows certain Pokemon to evolve. In Pokemon Diamond, Shiny Stones may be found on Iron Island and on Route 228. It may also sometimes be obtained through the Pokemon ability Pickup.
togetic-togekiss
I pretty sure Roselia evolves into roserade using a shiny stone
Roselia to Roserade and Togetic to Togekiss
use shiny stone on second stage of it
you use the shiny stone to evolve togetic into togekiss and i think there are a few others but that's the one i remember, i lost my diamond so i haven't played in awhile :\
in Pokemon diamond and pearl, its in iron island