I'm surprised there isn't a Rosie review already.

Rosie Cotton is amazing, and an absolute auto-include in Hobbit decks because of the versatility she brings. As a 2 cost 2 ally, she is as wonderfully cost efficient as the best Spirit allies and would fit in any deck even without a Hobbit hero on that alone. Where she shines is due to her ability, and the flexibility it provides players.

Because she can add her willpower to any attribute for a Hobbit hero, she becomes the equivalent of Celebrían's Stone, or Dagger of Westernesse, or Gondorian Shield. Except you get to decide which you need in any given round, and because the ability is an action, you can make that decision after staging so you know exactly which you need. She can also boost a defender after the shadow effect is revealed if there's a nasty attack increase.
In a Hobbit deck that doesn't typically have great defensive stats, sometimes you won't engage enemies even though you want to to proc Pippin and Sam's response, because you can't defend the attack. Rosie's ability enables the defense of some of those early attacks until you can find the Hobbit Cloak. Her ability is also not dependent on threat, so she makes a good backup to the Cloak for low threat enemies, or later in the game where your threat has crept up.

Outside of a dedicated Hobbit deck, I've used her as solely as a boost for Bilbo, where he was present simply for card draw. Would also work reasonably well with Sam in a similar context.

Fast Hitch lets her contribute to questing and combat (note the ability is once per phase). Anything that increases her willpower is great, Wild Stallion, Elrond's Counsel, The Arkenstone, Sword that was Broken are some I've used with regularity.
Note Red Book of Westmarch will only increase her willpower during the quest phase, so won't apply the boost to combat.

For fun and profit, use Sword-thain and then Rosie can benefit from the myriad of willpower boosting effects that only target heroes. Fireside Song, Celebrían's Stone, Song of Hope to name a few. MOTK will work here as well, but in my playing of it I found myself really hurting for actions until the hitches showed up, so overall would rather have her as an ally.

In a variety of ways, Rosie Cotton is very, very, very good. Her stats are extremely solid (2 cost for 2 willpower and 2 hit points is always great), with me especially appreciating her 0 attack and 0 defense, making her an extremely cheap Messenger of the King. She is almost always an auto-include in a deck containing a leadership and a Hobbit hero somewhere on the board (including most saga quests), where she shines with her extreme flexibility (be it post-staging willpower, post-shadow defense or attack).

That is her base usage, which would already push her to a very high position on this list, however there are so many situations in the game where she then shines especially. In every quest where there are willpower-reliant tests (like Mount Doom or A Shadow of the Past), you can often get double-usage out of her willpower (provided the boosted hero has any form of action advantage) and can adjust your willpower on demand post-test (provided you have an action window then).

Speaking of action advantage, Rosie Cotton is a prime target for that as well, being then either able to use her ability twice (once during the combat and once during the quest phase) or questing and using her ability once. Any kind of willpower boost is also insanely good on her, often then being utilized and useful two or three times (as opposed to just once compared to most characters).

With all that in mind, she is not just a great ally in general and in a Hobbit deck, you can even build a whole strategy around her, with decks like this one even being top-tier questing decks revolving entirely around her ability.

Overall, Rosie is an insanely good card that combines a high versatility in a great variety of builds with having an extremely high ceiling when built around. She is in my opinion one of the very best hobbit allies in the game (in a stacked pool also including cards like Halfast Gamgee, Gaffer Gamgee, Pippin and Merry), one of the best Messenger of the King targets out there and only finds herself third on this list because of the insanity that is Faramir and the prevalence of Halfast Gamgee as a Messenger of the King.

Rating: 9.5/10

Decks of mine using Rosie Cotton

All my card ratings