An emphatic first half display was the foundation of the victory for Paulo Fonseca's side, as Bryan Cristante, Edin Dzeko, Mkhitaryan and Justin Kluivert all found the net before the break.
Domenico Berardi scored two fine second half goals - one a free-kick, the other a sweeping counter-attacking move - to drag Sassuolo back into the contest, although they never seriously looked like pulling off an incredible comeback.
Roma are back in action at the Olimpico on Thursday, as Istanbul Basaksehir visit in the opening group game of the Europa League.
If the second half performance was evidence that there are still things to be worked on, then the first half display will at least have encouraged fans about the direction the team is going in. Roma seemed almost unstoppable, carving Sassuolo out at will.
The Giallorossi could have had a penalty inside the first 100 seconds of the game - only for VAR to lead the referee to amend his initial decision. But Cristante headed the side in front from a corner soon after, and from that point the side did not look back.
A sublime low cross from Kolarov then allowed Dzeko to strike to make it two, before Lorenzo Pellegrini - who had turned in the corner for the opener - notched his second assist of the night with a measured pass that Mkhitaryan lashed home.
When Pellegrini then split the Sassuolo defence open to allow Kluivert the space to run through on goal and convert, he had his hat-trick of assists.
After the break, perhaps relaxed by the scoreline, Roma continued to threaten - they hit the post twice in the first five minutes after the restart - but slowly found their opponents clawing their way back into the game.
But the side remained resolute despite Berardi's goals, continuing their unbeaten start to the campaign - and adding a first win to their tally.
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