The 37-year-old mother of one has not played since a hard-battled three-set win over Petersen in the second round at the Miami Open in March before pulling back with knee damage.
The 23-time Grand Slam champ — presently positioned eleventh — additionally pulled back from Indian Wells in March whining through ailment.
Viewed by her significant other Alexis Ohanian, Williams multiplied blamed on her first match point yet fixed triumph on her second against her 58th-positioned rival.
A four-time Rome champ Williams keep going won on the red dirt of at the Foro Italico in 2016. She will play either her more seasoned sister Venus, who got a special case section to the competition she won in 1999, or Belgian Elise Mertens in the second round.
Ought to Serena and Venus meet in Rome, it will be their first gathering on European earth in almost 17 years.
Their keep going gathering on red mud came at the 2002 Roland Garros last.
In the interim, Punch reports that Serena Williams is planning for the French Open not long from now where she could coordinate Margaret Court's record of real singles titles.