For allowing access to other roles for accessing Extension Manager you may need to follow the below steps.
- Navigate to Customization > Scripting > Script Deployments
- Search for the three following scripts:ID: customdeploy_ext_mech_installer_eventID: customdeploy_ns_sc_ext_mech_uiID: customdeploy_ns_sc_ext_mech_services
- For each, click Edit
- On the Audience sub-tab, ensure to select your chosen role from the Roles sub-list
- Click Save