Edin Dzeko scored the only goal as Roma made it three straight 1-0 Serie A wins in 2017 against Cagliari and kept the pressure on leaders Juventus.
The capital club might have paid for slack finishing, with Diego Perotti and Bruno Peres missing presentable opportunities, but Dzeko outmuscled Nicola Murru to volley in Antonio Rudiger's cross from close range.
That made it 20 goals this season for the Bosnia-Herzegovina international and a club record-equalling 13th consecutive home win in Serie A
Dzeko also hit the bar before Cagliari ended the contest with 10 men after Joao Pedro kicked out at Kevin Strootman in stoppage time.
Defending champions Juventus, who beat Roma's local rivals Lazio 2-0 earlier on Sunday, remain one point clear at the summit with a game in hand.