Halep was last featured in the French Open where she lost to Poland's Iga Swiatek 6-1, 6-2 in the fourth-round clash.
Iga Swiatek, the only teenager who reached the fourth round, avenged a crushing defeat by Simona Halep at the same stage last year.
The 34-year-old Nadal next takes on 74th-ranked Italian Stefano Travaglia, who reached the last 32 of a Grand Slam for the first time after beating Kei Nishikori in five sets.
Top-seeded Halep won 10 straight games in beating Sara Sorribes Tormo 6-4, 6-0 to reach the second round of the French Open on Sunday and extend her winning streak to 15 match
Serena Williams can never be discounted as she launches another bid for a record-equalling 24th Grand Slam singles crown, but Roland Garros is the American's least successful major.
This time, Halep and Djokovic each collected a winner's check of about $240,000, but Djokovic got slightly more than she did.
World number two Halep, 28, was competing in her third Rome WTA final, having finished runner-up in 2017 and 2018 on the clay at the Foro Italico.
Halep, who is actually on an 11-0 run overall stretching back to February, recovered an early break in the opening set and then overpowered her 29th-ranked opponent the rest of the way.
Some of the cynicism around the restarting of tennis can be attributed to Novak Djokovic's ill-fated Adria Tour after the tennis star got infected with the virus.
Halep said that she's 'looking forward' to playing the event in 'beautiful' Prague, and will be making her tournament debut.
Former world number one faced a semifinal exit at the hands of Spain's Garbine Muguruza in the Australian Open.
Halep captured her second career major with a 6-2, 6-2 victory, adding a maiden Wimbledon to her 2018 Roland Garros triumph.
Alexander Zverev, playing for the third day in succession, was shocked by Ernests Gulbis, ranked 138, in a gruelling five sets.
Simona Halep is the first women’s top seed to lose to an unseeded player at Wimbledon for 10 years.
Hsieh Su-Wei's 3-6, 6-4, 7-5 win sent French Open champion Halep crashing out in the third round on Saturday.