The visitors went into the match holding a 5-2 aggregate advantage following the first leg at Anfield and padded that lead in the ninth minute when Sadio Mane calmly dispatched a Roberto Firmino assist to put Liverpool up 1-0.
The strike made Liverpool's trio of Mane, Firmino and Mohamed Salah the highest scoring threesome in Champions League history with 29 goals, surpassing the 28-goal mark set by Cristiano Ronaldo, Gareth Bale and Karim Benzema in 2013-14.
Roma were back on level terms minutes later through a bizarre Liverpool own goal as Dejan Lovren's attempted clearance hit teammate James Milner in the face and went back into the net to make it 1-1 on the night.
Jurgen Klopp's team effectively finished off the tie in the 25th minute when a poor headed clearance from the Roma defence fell right to Georginio Wijnaldum and he nodded home from close range to put Liverpool's aggregate lead at 7-3 before half-time.
Needing four goals to force extra time, Edin Dzeko popped up to settle and score his team's second on the night after Loris Karius redirected a Stephan El Shaarawy shot into his path.
Radja Nainggolan then fired home a superb goal from distance and added another from the penalty spot to further cut the deficit and put gloss on the final scoreline, while also making it the highest-scoring UCL semifinal aggregate finish in history.
But it was too little too late for Roma as Liverpool saw out the result to book a spot in the final against Real Madrid on May 26.