Hi Shweta,
There are no network level roles at WordPress. Be aware that when you work with roles at the “Network Admin->Users->User Role Editor”, you work with roles of the main site of a network really. “Network Update” from there overwrites roles of any other subsite of this network with roles from a main site of that network. So any changes made to the roles at subsite are lost after you click ‘Network Update’. All subsites get an exact copy of capabilities and roles from the main site.
It’s possible to send to subsites just one role from a main site and do not touch any others. Go to the main site “Users->User Role Editor”, select role, turn ON “Apply to All sites” option at the top of a page and click “Update” button. Only current role will be replicated to subsites in this case.
