Roc definitely still needed Dame. He's the one that fought for the label to get a better split for the Hard Knock Life Tour. Def Jam was trying to pay the artists evenly for a tour that was built one Hov's album. Dame was storming offices and fighting for Jay as the headliner to get a bigger share. He was seen as an "assh*le" because he wasn't willing to accept the "n*gga deals" they were throwing at him. He fought for Jay, for Beans, and definitely for Kanye. So this is someone that was very vocal about his artists always getting their fair share. He even went back and paid Cam's debt that he owed to Undeas. So that Cam could be free and start recording again.
Problem is, he was fighting the kind of people who aren't used to black executives defending themselves and going to war for what was rightfully theirs. Those people don’t like that. So they told Jay that once he was done with Dame, they would take care of him. And they threw Jay deals and an office job, and Dame was gone. So yeah, it's about loyalty. And everyone isn't really with that, if there's a check elsewhere for them.