I spoke to the vet, and she said that it sounds like it would be a good idea to give Rosie subcutaneous fluids twice daily. I will give her 75-100 ml's every 12 hours. If Rosie seems too stressed by this, or if she starts to look or sound like she is getting too many fluids, then I will go back to once daily.
I already gave Rosie her first round of fluids today. Before I did so she was starting to look a bit more lethargic and was refusing food, but after receiving the fluids her appetite picked up again and she made her way to her food bowls (which are roughly a foot away from her on her beloved couch) and lapped some up.
Of course, if Rosie starts to decline and the fluids stop doing the trick, I will take her back to the vet for more IV fluids and any other further treatment she might need. I hope that won't be the case, though, and I would love to see her return more and more back to her old self. I know that pancreatitis is a serious medical condition that can may take a cat (especially a geriatric cat) some time to recover from, but regardless I will continue watching Rosie like a hawk.