Thanks for the information.
URE is not network activated at your WP multisite. Thus you have to work with URE settings separately for every site where you activated URE.
I went to the main site “Settings->User Role Editor->General” tab and found that “Show Administrator role at User Role Editor” checkbox is turn OFF as it is by default. URE hides ‘administrator’ role from the user in this case. I turned this checkbox ON and ‘administrator’ role is available for selection now at the main site. If you need the same at the subsite you have to make the same at the URE settings.
Other way – network activate URE and make needed settings once at the Network Admin->Settings->User Role Editor.