hello, the only solution I have for your problem would be to not make the whole rollover in Fireworks.
I'm very new to this and dreamweaver & have found it easier to make a file in fireworks that is the exact size of one part of a button (ie what will be the mouseout version when it goes into a web page)
I then copy this and save as another name & make the changes in this file so it becomes the mouseover version for when the images are imported into the web page package.
maybe this is not using fireworks to it's full potential but it seems to save file space and you know exactly where you are with everything...
not sure if that helps, I'm still pondering on what to do with my opacity stuff...
Josie