You can't. But I know how to go down it!
When your near the Ranger Union, and you have a Floatzel or Empoleon, go to the half built bridge and you'll have a "?" above your head. Click on Floatzel or Empoleon with your stylus or finger and you'll be able to surf on Floatzel or Empoleon and you'll go down the waterfall!
you dont
It is obtainable in vien forest near Regirocks area, but you can obtain Roserade in Vien Forest after you completed the quest "Roserade Red, Roserade Blue".
Vien Forest is north of Vientown where you get to be a Ranger.
You can find it at Vien Forest.
its between pueltown and vientown
get hm waterfall on route 18 and use it up the waterfall in lostlorn
i have no clue my fellow brotheran
you go back where you had capture it
in vien forest
theres no such place on Pokemon ranger or do you mean vien forest
in the hia lake and in a cave in vien forest
he's in the vien town forest
That'd be Weedle which is within the trees in the Vien Forest.