Migration

When there are 2 forest with 2 way external trust how will the file permission work while migrating a member server from forest A to forest B.ie using admt v3 all users have been migrated along with translate profile to new forest B (with SID History ).But the roaming profiles are stored in a member server of the forest A.If this member server is joined to forest B will the users get their roaming profiles.(when the forest A is demoted or removed).What should i do to get the roaming profile working.