As we did with the Pittsburgh Steelers, everybody if they’re smart uses “initial” to preface the 53-man roster. That’s because the 53 players who survive cutdown day are almost never the same 53 who open the season. Teams always look over the waiver wire, hunt for straggling veteran free agents, and seek trades to fill out weak areas of the roster.
In order to add a player, you need to subtract one, so rosters need to have an order of priority. Position, health, flexibility, and special teams contributions factor into that, but generally, you know who the vulnerable players are.