by when do teams normally finalize their roster signings and trades? before training camp?
I *think* it has to be done by the the first regular season game, but likely close by training camp.
and training camp starts?
I thought they could trade right up to the deadline in February, but just don't often do so early in the season?
Right, but we are talking about when the roster has to be trimmed to 15, there's multiple other ways to do that besides via trade.
Training camp typically begins around Oct 1 and 1st game around Oct 31.