Technically this isn't limited to just her role power. I am just confirming that when she utilizes the Staff of power for the second power that she can fish any spell out of her deck and recharge/discard any boon.
The Staff text reads:
For your combat check, reveal this card to use your Strength or Melee skill + 2d6; you may additionally discard this card or a spell to add another 2d6.
Reveal this card to search your deck for a spell and draw it, then discard a spell.
If i'm understanding this correctly, this is part of the cost to active the power. And not just a price you pay after activating the power. Or better put, Talitha with the right power feats could recharge any card she wants to fish a spell out of her deck.
I would read that as discarding a spell for a power on a Staff, so yes, I agree that Talitha can recharge any card (with that staff) to search out a spell. Pre-Role, she can effectively recharge any blessing to do the same thing, since she can bury blessings to do that inherently, then recharge buried blessings trivially.
MM Ahmotep would also be able to do the same thing even without a power feat spent on a Role card, and has the improbably powerful Eldritch Scion Role (where she can draw spells from her discard pile by recharging other spells, effectively ensuring that spells can copy each other and effectively self-heal herself every spell every turn, if desired).
In short; certain Magus characters are really really strong. The Magus Class Deck is one of the strongest Class Decks out there.
That's also how I read and played it.
I picked Talitha's other role, Holy Avenger, so I missed out on that particular feat. Instead, I used the "...bury a blessing ([x] or any boon)". Typically i buried a blessing and later recharged the blessing on a check. Then activating staff of power to search my deck and shuffle my deck (and thus, now I don't have bottom-decked blessings).
Or, I'd just bury every blessing to get +10 to any check with the Holy Avenger's feat "For each of your buried blessings, add 1 to your check that invokes the Outsider or Undead traits ([X] or to any of your checks)." This made it easy to acquire junk which I could then bury to search my deck with the staff of power. And since my Arcane was +16 I pretty much recharged any spell I played so I never needed to worry about them getting discarded.
Nothing to add to the rules question itself; it was covered well above.
PACG has no notion of “cost to activate” vs “effect of activating.” If you have a power that cares if you played a staff and a spell was discarded, you treat those as separate conditions and if both are fulfilled for any reason, then the power is usable.
The Staff Master power reads
When you would discard a spell for a power on a boon that has the Staff trait, you may discard or bury (☐ or recharge) a blessing (☐ or any boon) instead.
This power is asking two things (as above):
1. A power on a boon with the Staff trait is being used.2. In the course of resolving that power, a spell was discarded.
If both of those are true, regardless of the reason or timing the spell was discarded, Talitha’s power activates. It doesn’t matter if the spell discard is a “cost” to activate or not, because PACG has no notion of “cost” in the rules. For condition 2 above, it’s not a requirement that the Staff itself is making you discard a spell, just that the discard happens because of using that Staff power.