Osula was as you said very likely, and I think his suspension kind of made it inevitable, he hasn't made the impact expected and isn't available for 3 games and he wasn't brought in by Warne Given the way the club seem to do business, I would expect Warne to have been planning for that.
Roberts is likely to stay, he isn't getting games because Warne is rightly reluctant to change a winning team and a defence which is keeping clean sheets. If the players happy then wouldn't see an issue, there is no guaran tee he would get more game time elsewhere and clubs no the set up at derby is very good. But we shall see.
I reckon Lampard will be sacked before Dobbin goes back to Everton!