A user with the role Operator can Start/Stop servers and hosts but a with user with role Deployer can't although the Deployer role should have all permissions of Operator as described in documentations.
http://planet.jboss.org/post/role_based_access_control_in_wildfly_8_tech_tip_120
http://docs.wildfly.org/13/Admin_Guide.html#rbac-roles

If the user with the Deployer role also gets the Operator role then the user can Start/Stop servers and hosts.