On page 24, under “Creating a Role”, there is a bit which says:
We will define the property sys_defaultcommunity for this Role, with a value of Enterprise Investments. This property ensures that users will be logged in to the Enterprise Investments Community when they log is using this Role. Note that we will create the Enterprise Investments Community in a future procedure.
At present, the defaultcommunity is a dropdown which pulls from the current list of communities, so you are able to create the Role before you create the container community as the documentation suggests.