I've never seen a green cheek like that, is it possible Rose is a hybrid of some sort?
Nada. I've done a lot of research on both hybrids and mutations, this bird is/has neither. The discoloration here is the result of "red suffusion", where green feathers start to turn red. It's typically due to poor diet or some kind of organ problem, though I'm sure there can be other causes as well. If you ever wonder if a bird is a hybrid, the best rule is to look at how sharp a bird's markings and color is - hybrids will always be a mix of the two parent species, meaning these features will be blurred together.
Red suffusion tends to get mixed up with mutations more, some breeders will even try to sell them for more money when all they have is an ill bird. In these cases, look at the bird's feather quality and how symmetrical and evenly spread the color is. The bird pictured is a wild-type green cheek conure with a similar condition.