When and where can scrolls, curses, and potions be used?
Thus far, the best use cases I've seen have been that scrolls and curses can be used at any time whatsoever even if you aren't in an adjacent room. You do have to read some of the cards carefully, as it may determine before or during a combat phase. Potions are still as they were, only adjacent or same room. With the portal expansion, potions can be used across portals.

There's an older discussion I found on Munchkin Quest forums that seems to back up this train of thought. Seems to also be backed by Steve Jackson.