They usually release rooms 60 days in advance, but I have sometimes gotten rooms earlier than that in the summer. It could be that those rooms come from members who are trading, or perhaps they can tell from the reservations they already have...
I don't know about developer inventory but it appears to be close to a year out. For points given up for trades, it appears to be up to 10 months or so. For non used member owned inventory (breakage), it's 60 days out.