It plays like an inverted Evoke, where the creature is guaranteed but the spell requires a premium
Despite falling short of the $100 mark, Rosa might see some exceptional highs in the future, though be aware that they likely won't come without some major dips first
It's only three mana against a pesky one drop
Optimally, those 1/1 rats will have power boosts too, such as from Gnawing Crescendo or Imodane's Recruiter
Even mechanics as simple as cantripping (a spell drawing you a card in addition to another effect) were thought to be a thing of the past, since cantripping was used in Ice Age, Alliances, and Weatherlight
Somewhat early in design, someone submitted a punisher card, punisher' being slang for cards that forced your opponent into a choice between two bad things. This was a great flavor for villains, who love nothing more than forcing heroes into ugly choices