Rosellas are native to Australia and nearby islands, where they inhabit forests, woodlands, farmlands, and suburban parks and gardens. They are confined to the coastal mountains and plains and are absent from the outback. Introduced populations have also established themselves in New Zealand (notably in the North Island and in north Dunedin) and on Norfolk Island.
Ranging in size from 26–37 cm (10–14.5 in), rosellas are medium-sized parrots with long tails. The feathers on their backs show an obvious scalloping appearance with colouring that differs between the species. All species have distinctive cheek patches. Sexual dimorphism is absent or slight – males and females generally have similar plumage, apart from the western rosella. The juveniles of the blue-cheeked species, and western rosella, all have a distinctive green-based plumage, while immature plumage of the white-cheeked species is merely a duller version of the adults.
Rosellas feed predominantly on seeds and fruit, with food held in the foot. They enjoy bathing in puddles of water in the wild and in captivity. Rosellas scratch their heads with the foot behind the wing. Mutual preening is not exhibited by the genus, and the courtship display is simple; the male waves his tail sideways, and engages in some head bobbing, and the female reciprocates.
Like most parrots, they are cavity nesters, generally nesting high in older large trees in forested areas. They generally have a clutch size of several eggs which are incubated for around 21 days by the female alone. The male feeds the female through this time and for some time after incubation concludes. Quickly covered in a white down, chicks take around five weeks to fledge. The more colourful rosella species are popular as pet parrots and also as aviary birds. They can live for longer than 20 years, and they are relatively easy to breed. All have a reputation for being aggressive in captivity, and are hence recommended be kept separate from other caged birds.
Their diet in aviculture includes seeds, fruit such as apple, pear, and grapes, and vegetable matter such as lettuce, grass, and silver beet.