I found that taking a different route to access the roles works much better via the f.input
Here is the working code:
form do |f|
f.inputs "Admin Details" do
f.input :email
f.input :first_name
f.input :last_name
f.input :alias
f.input :bio
f.input :password
f.input :password_confirmation
f.input :roles, :as => :check_boxes
end
f.actions
end