Lorenzo Insigne’s effort was deflected and Higuain acrobatically volleyed it in with a scissor kick to give Napoli the lead in the third minute.
Inisgne then drilled the ball just wide of the left upright before unleashing a curler which Roma goalkeeper Morgan De Sanctis did well to fingertip around the base of his post.
Moments later, Callejon’s fierce strike crashed off the crossbar.
Roma began to get more into the game but didn’t have a sight of goal and it was Napoli again which went closest toward halftime, with Hamsik also hitting the crossbar after De Sanctis had denied Higuain.
Roma came out fighting after the break and Alessandro Florenzi fired wide before forcing Napoli goalkeeper Rafael into a smart save.
However, it was again Napoli which had the best opportunity shortly after the hour mark when Kalidou Koulibaly led a rapid counter attack and set up Callejon, who dinked the ball over De Sanctis only for Radja Nainggolan to sprint back and clear off the line.
Napoli did score a second six minutes from time as a delightful diagonal pass from Higuain allowed Callejon to slot past De Sanctis.