Roberts said he had decided to come forward out of fear the FBI would come to question him over the joke after millions of UFO conspiracy theory fans signed up to invade the top-secret US Air Force base, the Daily Mail reports.
"I was like, the FBI is going to show up at my house and it got a little spooky from there," he said.
More than 1.5 million people had signed up as "going" to the "Storm Area 51, They Can't Stop All of Us" Facebook event scheduled for September 20, with another 1.1 million "interested."
On Monday Roberts contacted news site NPR under they pseudonym "Val", insisting the Facebook page was only 'satirical.'
"I just thought it would be a funny idea for the meme page," Val said via Facebook Messenger.
"And it just took off like wildfire. It's entirely satirical though, and most people seem to understand that."
Area 51' is the popular moniker for the Nevada Test and Training Range, where the US Air Force has tested top-secret aircraft since the 1950s.
Famous machines developed there include the U-2 and SR-71 Blackbird spy planes and the F-117A Nighthawk stealth fighter.
Conspiracy theorists claim the base was used to research an alleged crashed alien spacecraft at Roswell, New Mexico, in 1947.
Roberts said his prank was inspired by podcaster Joe Rogan's recent interview with Bob Lazar, the man who claims he worked at Area 51, reverse-engineering alien technology from one such flying saucer.
Lazar's claims were first publicised by KLAS TV in 1989. Most recently he was the subject of the 2018 film Bob Lazar: Area 51 & Flying Saucers by conspiracy theory documentary-maker Jeremy Corbell.
A company called Area15, which operates a shopping mall in the area and runs live immersive experiences, was planning to livestream the assault on the 'top-secret' military base after its bosses' curiosity was piqued.
The company wrote in a post shared on Facebook and Twitter: "Okay. Now we're curious too about what's going to happen on 9/20 at the storming of #AREA51.
"We're going to live stream the 'event' here at #AREA15 to watch what goes down. And, of course, costumes and tin foil hats are required."
"We will all meet up at the Area 51 Alien Center tourist attraction and coordinate our entry," the event description says.
"If we Naruto run, we can move faster than their bullets. Lets [sic] see them [sic] aliens."
The phrase "Naruto run" refers to anime character Naruto Uzumaki, who is known for a running style that has his body tilted forward and low to the ground while his arms are stretched out behind his back.
The Area 51 Alien Center is a truck stop on Interstate 95, about an hour's drive from the Nevada Test and Training Range - which contains Area 51.
Despite the fun nature of the event, a spokesperson for the US military warned off would-be UFO raiders.
A spokesperson told the DailyMail.com: "[Area 51] is an open training range for the US Air Force, and we would discourage anyone from trying to come into the area where we train American armed forces.
"The US Air Force always stands ready to protect America and its assets."
The U.S. Air Force has warned people against participating in an internet joke suggesting a large crowd of people "storm Area 51," the top-secret Cold War test site in the Nevada desert. Photo / AP
The last known person who went hunting for aliens at Area 51 was shot dead by guards back in January.
What takes place inside the heavy-duty fence at Area 51 has remained a mystery to anyone without high-level security clearance, save for a few photos taken illegally by curious conspiracy theorists.
In 2013 the US government admitted that the base is a secret intelligence hub when the CIA released an official history of the U-2 and OXCART projects, along with aerial photos of the site.
NTTR experienced a rare security breach in January when an unidentified male sped through a checkpoint at the entrance. Guards and Nye County police chased him at high-speed for about eight miles before he came to a stop and exited his vehicle.
He began advancing toward officers with an 'unknown cylindrical object' in hand and did not heed verbal warnings to stop, so security officials were forced to open fire.
