De Rossi was rised as a tipical CM and later transformed to DLP, then to Left wide mid, then to bwm and now he plays more of Anchor Man and dlp as in Roma he drops really deep when defending.
I think you guys are mistaking the b2b with the tipical CM role. The b2b is a role that includes a lot of pressing and moving into channels or ariving late in the box. De Rossi did not press much futher up, neither he moved into some channels to look for goalscorring opportunities. Rather he just dropped deep to help Pirlo and had more defensive duties to cover the zone left from Balzarreti.
Ambrosini is a Anchor Man or a tipical CM connecting the game with simple passes and movement. Started as CM for Milan initially. Motta and Stankovic are playmakers - holding the ball, running with it, looking to distribute well. The only CM I can call to be a box2box in Italy was Perotta, althoug he would be given different instructions in almost every match he played.
GodCubed, they were def not Wing Backs. Prandelli is very good to make the difference when he needs to use wingbacks and fullbacks. Zonalmarking wrote a very good article about it recently. Although it is very dificult to make the difference, usually the wing back stays much further up and is pressing early, while the full back stays deeper (when defending) and is pressing rarelly.