Skip roles in environments based on chef guards

Hi ,
I am looking a flag to skip one of the role in environment run_list. Can you please suggest how can we make it.

ex:
run_lists": {

   "infrastructure_run_list": [
  "role[rfds-chef-xx]",
  "recipe[unix_base]",
  "role[n4_app_<ENV_LONG>]",
  "role[domain_n4_<ENV_LONG>]",
  "role[merch_nxxx]"
],

}

here I want to skip the role: "role[merch_nxxx]" based on the flag