Community and Safety features
From Roll20 Wiki
Reporting
It's important to the Roll20 team that our Forums, Private Messages, Looking for Group, and games bring everyone to the table. If you find an interaction to be in conflict with our Code of Conduct, please let our team step in. This can be done through the Report function.
The link to use the Report function can be found just below the name if the individual user and just above their message. Once clicked, you'll be asked to include the reason why you're reporting. Type your answer, and click "submit." The moderators will be notified, and take appropriate action.
Blocking
It is also possible to remove the option for another user to interact with you. Blocking a user will prevent you from receiving PMs from that user, and hide all (past and future) of their forum posts (except for past posts on Campaign Forums on Games that you own and Looking for Group Listing forums).
To block a user, click the Block link on their User Profile page. It is the last link under their Avatar. If you want to unblock someone, you can do so by clicking the Unblock link in the same place where the Block link was.
Kicking from Games
If a player on one of your games is no longer welcome, you can remove them from the game by opening the Game Detail page, moving your mouse over the Player avatar, and clicking on "Kick from Game."