No one in football is immune to being fired. No one. It's entirely possible that Ross will fire everyone if this season continues to be this embarrassing.
Consider the following:
1. A bad enough season means reduced revenue as people stop buying gear and tickets. Weigh the value of the contract buyout vs the declining revenue.
2. We don't know the money value of Flores' contract. Five years? If he's the least-compensated coach in the league (he probably is), then that's not a huge deal.
3. If Ross cleans house after the season he can deflect accusations that the team was losing intentionally by saying "Uh, wow, I said we were going to rebuild, not be the worst team in League history!"
While I do not think that Flores will necessarily be fired for a 1-15 disaster season, if this team continues to lose in insane blowouts every week, a move may be unavoidable.
Disclaimer: I am personally rooting for a full housecleaning that starts with Grier.