Roberts shared a screenshot of a notification he claims he received that said the event had 'been taken down by Facebook' because content posted to this event 'went against' Facebook's community standards.
The message also said the event creator is able to request a review if they feel the decision is 'wrong'.
"I never got any reason behind the event being removed," Roberts told CNET.
"I created a sister event which amassed about 15,000 people before being taken down for no reason."
The viral Facebook event was called 'Storm Area 51, They Can't Stop All Of Us' and had been scheduled for Friday 20 September at 3am.
Encouraging the masses to meet up at the mysterious US military site to find out what's really going on there and 'see them aliens', it had managed to garner the attention of more than two million attendees, despite warnings from authorities.
The event description said: "We will all meet up at the Area 51 Alien Center tourist attraction and coordinate our entry. If we Naruto Run [an attack inspired by Japanese manga, in which people run with their arms outstretched backwards and heads forwards], we can move faster than their bullets.
"Let's see them aliens."
After Roberts announced that the event had disappeared, many people weren't happy - with one Facebooker writing: "We don't need an 'event page' to do work. Everyone is still down, Facebook or not."
Someone else joked: "Doesn't matter if the event page is gone, the date has been carved in Stone tablets. This has reinforced my will to participate."
A third commented: "F*** that! We're still going."
Another added: "Damn bro I was just about to check the page out and it was gone! I knew they would do that, but was shocked it took this long."
A spokesperson for Facebook told LADbible: "This was a mistake and the event page is now available again."
While Roberts originally created the Facebook event as a joke, he told CNET he's been planning an actual, legitimate Area 51 festival in Rachel, Nevada, for 20 September - when the raid had been scheduled for - which would take place at a site that's not a top secret military base.
He claimed he created another Facebook event for this, but said this was also taken down by the social network.
"I think it's pretty reckless of Facebook, especially because I'm trying to direct people away from storming the base," Roberts said.
"And now I've lost my entire audience." Roberts still expects around 20,000 people to attend the festival.