More Complete Order Role ListOotP Film
Here's a larger list of the roles - not actors in them - that we were currently able to ascertain are in Order of the Phoenix; new/interesting ones at top. Note this is not complete, not confirmed by WB, of course may change with rewrites, and does not say anything about the actors playing these roles. Note it doesn't include most of the mainstays or students/professors whom you would expect in the film anyway.
Young James / Lily / Snape