Omegle.com is a site like chatroulette and it's one of the best webcam chat sites in the world.
Starting a random video chat on Omegle is just easy. Go to website and click to "Video" or "Text" buttons; if you choose video chat, you must also enable your webcam to work for people to see you, if you don't want them to see you, you msut not enable webcam to work.
After these steps, you may connect to chat with random people to chat. You can search people by interets area typing something or chat with College people if you have an email ended with .edu etc. and also you can chat on Unmoderated adult chat area also.

Unfortunately, there is not such an option on Omegle, you can't start a group chat or join on a group chat on Omegle.
You must search another chat groups like Camfrog, Paltalk or Tinychat etc. to get free chat on any group. Tinychat allows people to create their own rooms and you can join popular video chat rooms on Paltalk and Camfrog; you must download their apps also.