I don't know De Rossi's mindset but he must surely in the back of his mind be thinking about winning titles etc.. and I just cannot see him getting that anytime soon at Roma.
Look when Juventus and Milan went down for match-fixing, it was between Roma and Inter for the title but Inter came out on top. Now Juventus are back in the league and have just won the title. What must he be thinking?
I'm looking at it this way - If I played for City but was not winning titles or trophies then I would consider leaving, no matter how much I love the club being a die hard fan etc, my job as a professional footballer is to win trophies. I will always love City as a supporter and that support is lifelong, as a professional footballer it last nowhere near that long and my aim would be to win as much as I can in my career.
I might be looking to deep into this but why did De Rossi take so long in January to sign a new contract? Maybe it was just a wage issue, but I personally don't think he was convinced in coming to us then, while now he has seen us win the title - especially in that dramatic fashion - he might see us as a new direction in his career. Just my opinion.
We all don't know what is going on, just opinions at the moment guessed around quotes and articles.