"It's too early to talk about the title. All we can do is look out for how we develop as a team, work to improve and win every match we play. But now is not the moment to talk about the title," said Lukaku.
Antonio Conte's resurgent side wrapped the match up inside the first half, courtesy of an early Romelu Lukaku goal and a sensational strike by Khvicha Kvaratskhelia.
Belgium striker Lukaku completed a permanent move to Napoli from Chelsea on Thursday, ending a long period of limbo with the Blues.
Kevin De Bruyne was included in Belgium’s squad for next week’s Nations League matches but Romelu Lukaku was omitted after asking for time off to concentrate on getting fit after his move to Napoli, coach Domenico Tedesco announced on Friday.
Napoli have signed Romelu Lukaku from Chelsea, the Serie A club announced on Thursday, ending the Belgium striker's extended period in limbo with the Blues.
Paulo Dybala picked out Lukaku with a clever cross as the Belgium striker headed Roma in front in the fifth minute at the Stadio Olimpico.
Bruno Fernandes and Ricardo Horta netted the goals for Roberto Martinez's Portugal, with Cristiano Ronaldo not on the scoresheet, to end with 10 wins from 10 matches in Group J.
Lukaku grabbed his third goal in five league games for Roma after latching onto a clever pass from Paulo Dybala midway through the first half.
Belgium forward Lukaku rolled in Roma's sixth in the 82nd minute of a dominating performance in which talisman Paulo Dybala also got off the mark for the season with a brace.
Simone Inzaghi's side stay second and are three points ahead of local rivals AC Milan, who beat Monza 1-0 earlier on Saturday, but are a long way behind rampant Napoli after their 2-0 win at Sassuolo on Friday.
Inter Milan striker Romelu Lukaku said he is hoping to put his injuries and Belgium's premature World Cup exit behind him and return to form for the Italian club in a bid to discuss a permanent move from Chelsea.
Belgium should not blame Romelu Lukaku for their World Cup exit despite the striker's misses in the goalless draw against Croatia which sealed their fate on Thursday, said Timothy Castagne.
Romelu Lukaku trained on Friday ahead of Belgium's World Cup match against Morocco after missing their tournament opener in Qatar with a thigh injury.
Lukaku out of first two World Cup games: Belgium source Romelu Lukaku will not play for Belgium at the World Cup until at least their final Group F match against Croatia, a team source told AFP on Sunday.
Kevin De Bruyne’s mercurial talent is indisputable and Romelu Lukaku will be a powerful force up front, so the big question for Belgium heading to the World Cup in Qatar is whether they can get the best out of playmaker Eden Hazard.
Belgium coach Roberto Martinez says the absence of "irreplaceable" Romelu Lukaku from the World Cup would force his side to change the way they play, but the striker has not been ruled out of the tournament yet, team officials confirmed.
Romelu Lukaku has suffered a new hamstring injury less than a week after making his return to action for Inter Milan, the Serie A club said on Monday.
Romelu Lukaku should be available for Inter's Milan's Champions League clash with Viktoria Plzen which could seal the Italians' place in the last 16, coach Simone Inzaghi said on Tuesday.
Inter Milan made it two from two in Serie A with Saturday's comfortable 3-0 win over Spezia on Romelu Lukaku's return to the San Siro.