Constructing roles only with the include keyword

As the Puppet documentation states regarding roles, in rules  (https://puppet.com/docs/pe/2017.2/r_n_p_full_example.html#the-rules-for-role-classes), the only thing roles should do is declare profile classes with the puppet include keyword. That is, they don't themselves have any class parameters. Roles also shouldn't declare any component classes or resources—that's the purpose of profiles.