Please be aware that the follow has yet to be officially confirmed, therefore should be treated as a rumor.

A reputable video and DVD shop lists the following cast names under its Fullmetal Alchemist; Conqueror of Shambala DVD section (not released yet):

朴[王路]美 (Paku Romi / Edward Elric)
釘宮理恵 (Kugimiya Rie / Alphonse Elric)
大川透 (Ookawa Tooru / Roy Mustang)
内海賢二 (Utsumi Kenji / Alex Louis Armstrong)

Source:
Tsutaya >> link (jpn)

go on...

YAYYY!!! Mustang might be in it!!!!

yes!!! more!!! give me more!!

*shall keep in mind its rumor*

Ooh, exciting!

Roy and Major Armstrong!!!
YAY!!!

now add Michiko Neya and my life is complete >.>

From the Newtype article that was translated by Syca, we know for a fact that Al H., Ed, and Gracia Hughes (in AU form) are in the movie. They made a mention of discussing Roy and the others in the next issue, so we'll just have to latch onto Syca for a translation of that article when it comes out.

~Merc

Woot! So this means Roy might possibly be in it! Or maybe... his twin in Ed's world? Mwhahaha... that would be interesting.

I hope Winry is there. As well as Riza. It would be so empty without characters like them.

i actually held unto my seat while reading the list... i thought it would be a long one...

aww... still waiting for michiko neya and any riza hawkeye news >_<;;

Roy equals goodness... but if there's no Riza, I will be sad...