Assume capabilities passed to add_role should be granted

src/wp-includes/class-wp-roles.php

@@ -160,6 +160,13 @@ public function add_role( $role, $display_name, $capabilities = array() ) {
 			return;
 		}
 
+		foreach( $capabilities as $key => $value ) {
+			if(!is_bool($value)) {
+				$capabilities[$value] = true;
+				unset($capabilities[$key]);
+			}
+		}
+
 		$this->roles[ $role ] = array(
 			'name'         => $display_name,
 			'capabilities' => $capabilities,