Interesting change zahlman, but I'm not sure I want this card to be a curser in games without one. The idea is to turn an opponents attacks directly against them. The new non attack effect means a strategy for winning would be to buy a lot of rousers and copper, giving you a semi terminal apothecary engine that also nukes everyone elses next hand; not sure that's what I want. $2 or P sounds a bit wonky though.
I'm still not sure what to make the non attack part, but I like the idea of some symmetry. Another idea would be to have everyone discard actions, which benefits you (since this is a terminal drawer), and hurts everyone else. I'm not a big fan of big money strategies though.
I would think that all the faq problems would be solved by having it be similarly defined to Moat and Lighthouse, just in reverse; you play a virtual copy of the card, but you are not affected by it, only the player who discarded the card is.
Therefore:
*You can trash their treasures with Thief and Noble Brigand, but you don't gain them after they go to the trash.
*With Pirate Ship and Minion, you can choose for either nothing to happen, or the attack portion of the card. If you choose the Pirate Ship attack and it hits, you still don't get any tokens on your pirate ship mat.
*You can't gain any cards with Jester, but you can make your opponent gain cards.
*You can block Young Witch and Mountebank attacks using the methods specified in their cards.
*Mercenary does nothing, because the card doesn't affect you, so you can't trash the 2 cards necessary to activate the attack.
*You can't start a cultist chain with someone else's virtual cultist.
Also in the card as it's written in the OP, the only attack that doesn't get activated by Rouser is Scrying Pool. I prefer the use of "discarded" since it definitively has the self attack in a separate timeframe to the initial Rabble style attack.