Based on what we have seen (or more specifically, haven't seen) I would not expect Armond Armstead to be on the week one roster. Granted we don't have access to the medical reports and I didn't stay in a Holiday Inn Express last night, but I would speculate that at minimum Armstead starts the season on PUP.
Rob Gronkowski is in a different situation because of how valuable he is to the team, and from various reports we have a little bit of a timetable to base the amount of time needed to rehab, and the amount of time needed to get into football shape. With Gronk I am more inclined to place him on the Week One 53-man roster and just leave him as a game day inactive until he is ready to play.
With Armstead apparently unable to play this means the Pats begin the season with Vince Wilfork and Tommy Kelly at DT. While they are both very capable, Wilfork turns 32 this season and Kelly will turn 33. I want both of these guys to be fressh in the 4th quarter of games and as fresh as possible at the end of the season and in the playoffs. For that to happen then Marcus Forston needs to progress to a point where he can get plenty of snaps every game without a significant drop in production. I don't think any of the other defensive tackles on the roster (Cory Grissom, Anthony Rashad White, Joe Vellano, Scott Vallone) can be counted on for much at this point.