Hi Jack and welcome to the site.
You don't have to wait until sorting comes around to roleplay here.
We have a special area for unsorteds to go and roleplay and get to know other unsorteds.
Your character can also roleplay in the shopping areas and world areas - it's only Hogwarts that you can't until after sorting.
So there is still plenty for you to be able to do.
When I first started I roleplayed on the express with my unsorted student and that was tons of fun.
We have a plot development area where you can post seeking someone for certain types of roleplaying ideas you have and a character / roleplay developing area as well. All of which can be found in the site documentation that Sir Kaitlyn linked you too.
We also have a OOC area where you can pop along and chat with the rest of us, we're all friendly and respectful of one another. There are games and competitions to enter as well. So lots to keep you busy until sorting which is around January 10th or thereabouts. The school year is broken into 6 week increments with holiday time inbetween. Classes and exams all are part of it. The wait for sorting seems long but on this site, it is very much worth it.
Hope you have lots of fun here with us and once again ...
Welcome!
Lin