Because the ability it has to copy is "Only supereffective moves will hit" and since role play is not a supereffective move against it, it doesn't work.
You cant get Pokemon from Pokemon ranger to platinum!
you cant
You cant
you cant
you cant
I'm not to smart, but you can't get Trapinch and Pokemon Platinum is better.
you cant but you cant but if u trade it from heart gold to platinum then you have a groudon
you can
you cant
you cant!
you cant
You cant