means of communication designed to reach the general population
The doomsday groups could gain attention in many different ways. A sign of a doomsday group is murders. Murders always get on the news so this could be a way of them trying to get other peoples attention. Also an act of terrorism can be related to a doomsday group. They can cause acts of terrorism such as bombings to try and gain more attention to them and get the word out that they will go to extremities to do what they believe in. They even would end up kidnapping people to try and get their message across.
individuals of roughly the same age and interests.
The doomsday cult was a group of people who believed in Apocalypticism and Millenarianism. This is similar to a peer group because they were all interested in those two things. The cult was made up only of people who had interests in those and that relates this doomsday cult to a peer group.
stage during which children take on roles of others one at a time.
The parents of the children basically raise there kids to believe the things that this group of people believes in. Their kids will grow up believing all of this and when they are older they will end up being in one of these groups. The kids will think that all of this is right because it is what their parents have taught them.