Hi Leslie,
Re: the roommate notification - you can either be matched with a roommate that the CP picks for you, or you can be placed with someone you already know, as long as you have their full name and applicant number (which they receive with their acceptance letter). This will ensure that you know the person with which you will be sharing a room.
If you participated in the roommate notification, you can try to ask for a certain size/complex at check-in, and they may try to accommodate your request - it may or may not work. It never hurts to ask, though.
If you do not participate in the roommate notification, you can request a certain apartment complex and size at check-in. It is not guaranteed, but I think they try their best to accommodate your request.
Recruiting for spring would take place in the fall, but I am not certain of which month they start. Yes, they do give you an option to extend your program towards the last couple of months of your program, provided your record card is clean.