diff --git a/dlls/api-ms-win-core-winrt-l1-1-0/api-ms-win-core-winrt-l1-1-0.spec b/dlls/api-ms-win-core-winrt-l1-1-0/api-ms-win-core-winrt-l1-1-0.spec
index 74c9d27aae39cc144943aa97036c8d014b88eed1..978c3dc6d0703f711ef9dd1995c617af3580ce49 100644
--- a/dlls/api-ms-win-core-winrt-l1-1-0/api-ms-win-core-winrt-l1-1-0.spec
+++ b/dlls/api-ms-win-core-winrt-l1-1-0/api-ms-win-core-winrt-l1-1-0.spec
@@ -1,4 +1,4 @@
-@ stub RoActivateInstance
+@ stdcall RoActivateInstance(ptr ptr) combase.RoActivateInstance
 @ stdcall RoGetActivationFactory(ptr ptr ptr) combase.RoGetActivationFactory
 @ stub RoGetApartmentIdentifier
 @ stdcall RoInitialize(long) combase.RoInitialize
diff --git a/dlls/combase/combase.spec b/dlls/combase/combase.spec
index c238eb82db7f82cb3e1dda8771f13c73e8fbb16f..f42bdae605ba766bf7c510b797913303aa6d89e5 100644
--- a/dlls/combase/combase.spec
+++ b/dlls/combase/combase.spec
@@ -242,7 +242,7 @@
 @ stdcall PropVariantClear(ptr) ole32.PropVariantClear
 @ stdcall PropVariantCopy(ptr ptr) ole32.PropVariantCopy
 @ stub ReleaseFuncDescs
-@ stub RoActivateInstance
+@ stdcall RoActivateInstance(ptr ptr)
 @ stub RoCaptureErrorContext
 @ stub RoClearError
 @ stub RoFailFastWithErrorContext
diff --git a/dlls/combase/roapi.c b/dlls/combase/roapi.c
index f7862fb774a2a3c0732b70894d9f4842fd5074d2..bfd07fb3f4ed6d33fb5806fa4fc50aa0dd230a92 100644
--- a/dlls/combase/roapi.c
+++ b/dlls/combase/roapi.c
@@ -198,3 +198,23 @@ HRESULT WINAPI RoGetParameterizedTypeInstanceIID(UINT32 name_element_count, cons
     if (hiid) *hiid = INVALID_HANDLE_VALUE;
     return E_NOTIMPL;
 }
+
+/***********************************************************************
+ *      RoActivateInstance (combase.@)
+ */
+HRESULT WINAPI RoActivateInstance(HSTRING classid, IInspectable **instance)
+{
+    IActivationFactory *factory;
+    HRESULT hr;
+
+    FIXME("(%p, %p): semi-stub\n", classid, instance);
+
+    hr = RoGetActivationFactory(classid, &IID_IActivationFactory, (void **)&factory);
+    if (SUCCEEDED(hr))
+    {
+        hr = IActivationFactory_ActivateInstance(factory, instance);
+        IActivationFactory_Release(factory);
+    }
+
+    return hr;
+}