Sluggish and slow, Barcelona laboured through a first half hour in which neither side attempted much apart from occasional dives in the penalty area.
Edin Dzeko and Andrew Iniesta both went down looking, while Alessandro Florenzi hit the deck in the area with Nelson Semedo in attendance. The Dutch ref was unmoved by all.
Roma’s captain Daniele De Rossi hit an unstoppable shot into his own net to break the deadlock in the 38th minute of what had been a delicately poised game and a second own goal 10 minutes into the second half, this time by Greek defender Kostas Manolas, stretched the runaway La Liga leaders’ advantage.
Barca defender Gerard Pique piled more misery on the Italians four minutes later, mopping up on the rebound after Luis Suarez was thwarted by goalkeeper Alisson before Roma’s top scorer Edin Dzeko struck at the right end to give his side faint hope of a turnaround in the second leg.