Madden 10 Franchise: Why does the computer automatically sign rookies?

[NicholasJ]

I do not like the rookie's in Madden 10, so I never want to sign them to my roster. I do not see a button that lets me do that, so I just press start. The commuter promptly drops some of my players and signs the useless rookies. I release all of them and try fruitlessly to recover my woebegone players, having already being picked up by another team. How can I avoid this?