Roll20Con is a yearly gaming convention run by Roll20 since 2014. It's usually in October.

From wikipedia:

"Roll20 has held an online gaming convention named Roll20CON every year since 2016, consisting of an organized series of online games hosted on Roll20 and streamed on Twitch, along with other events. Roll20 has partnered with charitable organizations to run Roll20CON: The Cybersmile Foundation, an organization providing support for victims of cyberbullying, in 2016; and Take This, an organization focused on mental health in the gaming community, in 2019."

roll20.net/con usually gets updated on the latest con

2021

Likely to be sometime in October.

Past Cons

2019

Roll20Con 2019 was October 5-6.

2020

Roll20Con 2020 was October 23-25^source.

From the Blog Post:

"From October 23rd to October 25th, 2020, we’ll be celebrating the online TTRPG community with panels, discussions, and plenty of gaming, featuring some of your favorite games, streamers, and creators from the wide world of Roll20.

This year, in addition to the fun you’d expect from Roll20Con, we’ll be celebrating the first-ever RPG built from the ground-up for Roll20, Burn Bryte! Expect plenty of surprises from the Olaxis Galaxy over the weekend, including demos, streams, and more."