It is not love or peace or wartime that brings the four Houses of Hogwarts together. It is lack of gender equality.
Perhaps they were doomed from a start, as a magical race. Perhaps they aren't reproducing as fast as they used to. Whatever the reason may be, the fact is, Rose Weasley is the only female Gryffindor in her year. This is why she now shares a room with Katherine Finnigan, who is twelve and Rather Knowledgable. They share books and then they leave each other alone. It is a peaceful existence, for awhile, but Rose can't help wanting some adventure.
(If you are dying to know who else is in Rose's Gryffindor year, Michael Abercrombie, a short, nervous-looking boy, shares his dorm with Louis Weasley, her cousin, and William Wood, who has not once stopped talking about Quidditch since he arrived here.)
Likewise, Rowena Kirei and Molly Weasley share their own small dorm room in Ravenclaw, whereas Jacob Ackerly, Ethan Boot, and Scorpious Malfoy (organized alphabetically, like a true Ravenclaw would have it), share their dorm.
On the other end of the spectrum, Lydia Farai, Ava Goldstein, and Emma Zabini, three girls who are either destined to be the best of friends or the worst of enemies by the end of the year, are the Slytherin first-year females, but Albus Severus Potter must share his dorm with Cameron Goyle, a hulking twelve year old, whom Albus swears is part-giant and apparently only speaks in grunts.
The Hufflepuffs consist only of Joshua Davies, Daniel Finnigan, and Madison Macmillan, who will probably become important later.
This means that Rose and Albus shall have to seek friendships outside of their own Houses. Albus was really intending to do this anyway, but the introduction of Cameron Goyle, Mountain Man, has rather cemented this decision in his mind. His housemates seem friendly enough. Sort of. Kind of. The sideways glances and whispers of that's harry potter's son he could do without, but he'll take what he can get, really.
Rose Weasley will scorn the inferior boys in her dorm – something Katherine Finnigan will fully endorse – but she will not join the older girl in reviewing her homework from over the summer. Rose Weasley, with an entire free afternoon ahead of her, will go exploring. With Albus, who is sort of boring and bookish and apparently Slytherinish, which Rose finds very slightly disorienting. But he is still Albus, and she knows him, so off they go into the Wild Blue Yonder of Hogwarts School of Witchcraft and Wizardry.