Lazio have also won 2 match earlier this season and they are the current leader of the table. Besides Juventus, I think Lazio will also be a match that can prove that Mourinho is worthy of managing Roma. Without excluding other teams on matchday 3-5 then I believe Roma vs Lazio will be a good match too. I don't know, I don't think Mourinho deserves to be tested anymore when he's in charge of a team because he's had a good career before with several teams in Portugal, England, Spain and Italy.
Mourinho is very experienced. There is no doubt about this. But the Roma squad is not strong enough. The coach will determine the plan and strategy of the match. But winning the match is not easy without experienced skilled players in the team. While Roma’s performances are stable enough, they can’t win against strong teams. So they are lagging behind in the fight to win the title.