pc2246, the game will adjust your roster if your over the cap or don't have enough players. I think either after camp or the final pre-season game i can't remember for sure. You could lose some or all of your good players though. But sometimes there's no other way.
If your sure there is no way out of that teams cap situation, think about trading away your good assets for future draft picks only. So you can at least get something for them. Get what you can for your good players and trade away your current draft picks for future ones. Or trade away the players you just drafted when the draft is over but I've always found it easier to trade the picks vs players. After it's all said and done you might have a healthy set of draft picks for the teams future. This could give you a dead cap issue for the following off-season but it's workable. You can move a few of those future draft picks for future ones again. You should be in the clear after the 2nd season.
If you want to watch a top notch GM in action with this same situation follow setherick and his Paydirt team. (team link below) That team was in a similar situation that you are in and I had to tear that team down and do the same thing as stated above. setherick has taken over the team and is getting ready to parlay some of those picks and start the rebuild. This is one of the GM's in MFN that knows how to rebuild a team and I would highly recommend watching how he does it. It can be pretty satisfying taking a team out of the ashes sort of speak. This is one way to do it and there might be other strategies out there. Either way good luck and have fun with it.
https://paydirt.myfootballnow.com/team/22