The 35-year-old advertising executive on a first date fell after the railing on her 17th-floor balcony gave way.
The accident happened at an apartment building at 400 East 57th Street early Thursday.
"I have friends who live in that building, therefore everyone's concerned," said Fred Fox, an East Side resident.
From the rooftop of a building across the street, you can see the balcony of Jennifer Rosoff where she took a tragic fall in the darkness onto the scaffolding below.
"Just someone falling off a balcony sounds a little iffy," Fox said.
At this point the, the NYPD is calling this a tragic accident.
Sources say the 35-year-old sales director was on a date with man who lives in a building about a block away, when she went to her balcony for a cigarette and it gave way.
"We live in the same building, so I don't know him, but I know he lives in my building, and I hope he's okay," said Lana Tufo, an East Side resident.
Rosoff grew up in Melville, Long Island.
Eyewitness News spoke to her sister in Pennsylvania by phone.
"Really, she was a very well-liked person. She had a lot of friends, very wide circle of friends," her sister said.
Thursday night, those who live in the East 57th Street building were told not to use their balconies, as the building department tries to determine why Rosoff's balcony was not secure.
"She was a nice customer, she come in about two times a week," said Alfonso Bellbuena, a restaurant worker.
"I think they should have looked into before it even got to that, because a balcony just giving way doesn't sound right," Tufo said.
The Buildings Department is investigating what happened. The gray brick high-rise building on Manhattan's Upper East Side was built before World War II. Only the higher-floor corner apartments have balconies, and the city's buildings department ordered residents to stay off them.
A photo of the corner balcony of the apartment where Rosoff lived shows the top two metal railings bent down in a V-shape. Buildings officials took part of the broken railing to examine how it could have given way and plan to determine whether the other balconies are structurally sound.
In 2010, after a 24-year-old social worker fell to his death when the railing gave way at his 24th-floor apartment terrace, the city conducted safety inspections on hundreds of residences. Tenants at 16 buildings were ordered to stay off their balconies because they were deemed unsafe.
Some 800 building owners failed to file mandatory inspection reports on the safety of their balconies and terraces, officials found. It wasn't clear whether the reports were current at Rosoff's building.
Rosoff worked at a new media advertising startup called TripleLift.
"The entire company is distraught by the loss of Ms. Rosoff - she will be deeply missed," TripleLift CEO Eric Berry said in an email to Eyewitness News. "We offer our sincerest condolences to her family and friends during this difficult time. She was a well-loved and highly-respected member of our team. Her tremendous energy and humor brought so much joy to the office."
Prior to Triplelift, Rosoff worked at The New Yorker, Lucky Magazine and Cosmopolitan. She attended Tulane University in New Orleans, according to her LinkedIn account.
