Well, if Antonio Conte joins, I don't see him failing as BR did at Liverpool. He's a kind of José Mourinho, but a bit self-obsessed. Tactically, he'll be the best manager of the league alongside Pep.
It is not guarantee that he'll be Chelsea boss for long time like Ferguson at Man Utd, but in the short term he's definitely the best manager Roman could appoint. I definitely see Chelsea finishing in the top 4 next season with Conte on their bench.