In 2012, Craig Dunn wrote a blog post (http://www.craigdunn.org/2012/05/239/) that quickly became a point of reference on how to organize Puppet code. He discussed his concept of roles and profiles. The role describes what the server represents, a live web server, a development web server, a mail server, and so on. Each node can have one and only one role. Note that in his post, he manages environments inside roles (two web servers on two different environments have two different roles):

node www1 { 
  include ::role::www::dev
}
node www2 { 
  include ::role::www::live
}
node smtp1 { 
  include ::role::mailserver
}

Then, he introduces the concept of profiles, which include and manage modules to define a logical technical stack. A role can include one or more profiles:

class role { 
  include profile::base
}
class role::www inherits role {
  include ::profile::tomcat
}

In environment-related subroles, we can manage the exceptions we need (here, for example, the www::dev role...