Organizations: return organization roots for requests made by other accounts within the organization

moto/organizations/models.py

@@ -482,7 +482,18 @@ def delete_organization(self) -> None:
         self._reset()
 
     def list_roots(self) -> Dict[str, Any]:
-        return dict(Roots=[ou.describe() for ou in self.ou if isinstance(ou, FakeRoot)])
+        if self.org:
+            return dict(
+                Roots=[ou.describe() for ou in self.ou if isinstance(ou, FakeRoot)]
+            )
+
+        if self.account_id in organizations_backends.master_accounts:
+            master_account_id, partition = organizations_backends.master_accounts[
+                self.account_id
+            ]
+            return organizations_backends[master_account_id][partition].list_roots()
+
+        raise AWSOrganizationsNotInUseException
 
     def create_organizational_unit(self, **kwargs: Any) -> Dict[str, Any]:
         new_ou = FakeOrganizationalUnit(self.org, **kwargs)  # type: ignore

tests/test_organizations/test_organizations_boto3.py

@@ -189,6 +189,42 @@ def test_list_roots():
     validate_roots(org, response)
 
 
+@mock_aws
+def test_list_roots_for_new_account_in_organization():
+    if not settings.TEST_DECORATOR_MODE:
+        raise SkipTest("Involves changing account using env variable")
+    client = boto3.client("organizations", region_name="us-east-1")
+    org = client.create_organization()["Organization"]
+    org_roots = client.list_roots()
+    new_account_id = client.create_account(
+        AccountName="test_account",
+        Email="[email protected]",
+        RoleName="CustomOrganizationRole",
+    )["CreateAccountStatus"]["AccountId"]
+
+    with mock.patch.dict(os.environ, {"MOTO_ACCOUNT_ID": new_account_id}):
+        client_for_new_account = boto3.client("organizations", "us-east-1")
+        new_account_roots = client_for_new_account.list_roots()
+        validate_roots(org, new_account_roots)
+        assert len(new_account_roots["Roots"]) == 1
+        assert len(org_roots["Roots"]) == len(new_account_roots["Roots"])
+        assert org_roots["Roots"][0] == new_account_roots["Roots"][0]
+
+
+@mock_aws
+def test_list_roots_for_account_without_organization_exception():
+    client = boto3.client("organizations", region_name="us-east-1")
+    with pytest.raises(ClientError) as e:
+        client.list_roots()
+    ex = e.value
+    assert ex.operation_name == "ListRoots"
+    assert ex.response["ResponseMetadata"]["HTTPStatusCode"] == 400
+    assert "AWSOrganizationsNotInUseException" in ex.response["Error"]["Code"]
+    assert ex.response["Error"]["Message"] == (
+        "Your account is not a member of an organization."
+    )
+
+
 @mock_aws
 def test_create_organizational_unit():
     client = boto3.client("organizations", region_name="us-east-1")