I loved Roost, but I loved DH more and played that to death. I'm lucky that, for me, RO2 is running OK even though my system is junk. I love RO2, I love the depth of field, I love the cover system, I love the mantling and the different movement modes. Sure there are some things I don't like, and I'm hoping one day there will be a more hardcore option to get rid of them.
But my one gripe with RO2, and this may be for many reasons, is that there appears to be much more individual work. In roost, and especially in in DH, I always felt you had to operate as part of a squad. You had to stick close to your team mates or you were dead, but in RO2 I feel much more as if I'm on my own (though I like the extra voices!).
Maybe it's because it's new, maybe it's because reloads, etc are too quick, or maybe I've just been unlucky, but but I loved the way that even on pubby's in DH you could usually find a small squad to help you clear a street house by house, resupplying each other, offering covering fire, moving up squad by squad.
I hope it's just my bad luck but for all the graphics issues, arcade vs non arcade arguments, what made roost and DH stand out for me was the teamwork, and having read books like Company Commander this seemed to be just as it was described in the books.