Given the following User<>Project<>Permissions<>Roles Model, how to obtain a project's team members?

Question

Given the following:

class User < AR::B 
  has_many :permissions 
  has_many :projects, :through => :permissions 
end 
class Project < AR::B 
  has_many :permissions 
  has_many :users, :through => :permissions 
end 
class Role < AR::B 
  has_many :permissions 
end 
class Permission < AR::B 
  belongs_to :user 
  belongs_to :project 
  belongs_to :role 
end

I'm interested in creating a SCOPE in the project model (project.rb) that returns all the project's members (bassed on the permissions table <> users & role tables.

Desired output: user.name, role.name

Here's my scope in the model, which isn't returning the desired output:

class Project < ActiveRecord::Base 
has_many :permissions 
has_many :users, :through => :permissions 
 #Playing with Scopes 
  scope :teammembers, 
  Project.permissions.joins(:users, :roles) 
end 

trying to figure out how to get the output with ActiveRecord. Thanks