How to make uzie and azelf appear on the roaming Pokemon app in pearl?

Question

They are already out of their caves and I've encountered both of them outside of their caves. Does the app only mark the location of the last pokrmon from the trio? Do I just need to run into them again to make them appear on the app?

Answer 1

You can find all three at these locations:

Uxie: Lake Acuity (found at Route 217)
Azelf: Lake Valor (found at Route 214)
Mesprit: Once you have visited Lake Verity (found at Route 201) and interacted with it there, it will be roaming Sinnoh.

Only Mesprit is roaming Sinnoh. You can find the other two in their respected caves.
Hope I helped. :)