I've said this in other threads, but I think that even if EJ or Tyrod starts in Sept, Cassel is as close as we have to a lock on the QB roster. IMO the only way Cassel gets cut is if either, a) he throws caution to the wind (excuse the pun), stops being conservative in his play, and seriously, seriously implodes, or b) Tyrod, or EJ suddenly blow up and turns into a serious contender for franchise QB, rendering Cassel's veteran presence obsolete. Neither of those scenarios seem remotely possible at this moment, and neither would even guarantee Cassel's departure. At this point, Ryan/Roman have to believe that they can game plan for Cassel as a known commodity, and rely on his consistently mediocre performance, and veteran ability to run the offense.
And, when it comes to deciding the QB roster, I don't believe that cap space, dead money, salary, or any other financial issue will even be heard in the discussion.