How are you placing the rollover in the box? Is it inline, or simply a child element (drawn over the top of the parent box)?
If it’s inline, you’ll need to use the old-school Parameters interface in the Rollover Action. You will need to take your “over” image and export it from Freeway at precisely the same size as your normal image, then use the Rollover picker to select it.
Rollovers DO work on inline images, it’s just not as simple as stacking and grouping a pair of images and applying the Action.