Although I think you have a clock issue it would be good if you could give additional information about your system, then somebody supporting you has everything in one place, i.e.:
- Which 64-bit version of Windows ? 7, 8, 10 ?
- Which mainboard do you use ?
- Which graphic card do you use ?
- What kind of latency do you mean ? Can you describe it a bit more or give sound sample ?

If you use multiple cards, then they need to be synchronized.
Preferrably by the RME card as master (as it has steadyclock).
So you need to look into the handbooks how the cards can receive clock and how they are connected to each other. The interfaces receive clock on digital input channels like ADAT, SPDIF, AES, MADI.

If there are no digital lines in use between the cards (like ADAT, SPDIF, AES)
then the only solution is to use Word Clock.

You need to check whether all interfaces support WC.

I would try smth like this:
RME card: set clock to internal
Rosettas: set clock to WC

My suggestion implies that you need to perform a proper WC cabling.

>The solution was to connect the WC out from the Multiface II to the Hdsp's WC input.

I am astonished that the HDSP PCI card, which "drives" your Multiface II, does also have WC.
Or is the sentence not correctly typed ?

I thought the objective is to simply use the WC IN and OUT on the Multiface II.
What did you do exactly ?

> On the DSP software leave the Multiface's clock source as Internal and the AES Clock Source as Word Clock.

When I look into the handbook on page 18, then it seems to me, that you only need to set clock mode to "master".
Settings "Pref Sync Ref" make only sense if the device is not WC master. So any settings will be ok as it doesnt matter.

Could you pls provide a screenshot of driver settings dialog ?

I hope this works. I'm on my iPhone and don't know how to upload a pic!
http://imgur.com/a/PEIrd

I don't know which part you don't understand?
Did you noticed something wrong?
Can you tell me?

Wow!!!!
That answer really knocks me out of the ring!
My system is estable by now (cross fingers) and I' m happy with it. Any future issue you'll be notice.

Maybe I know now why.

Could it be the case that you are using 2 different RME products in your PC
- RME HDSPe AES and
- RME Multiface II

additionally the 2 Rosettas ?

Then you would have in total 4 devices which need to be synchronized.
Then it would make sense to have an additional AES tab in the RME driver settings dialog.
On the screenshot I see: "AES (1)" and "Multiface (2)"

This you didnt communicate in the description of your setup not very well and
confused me why you talked about settings about AES.
Normally I regard AES simply as an I/O channel on a card not an interface itself.

So you have 4 devices to be synchonized.

Then I would eventually use the AES Card as Clock master since this seems to be the newer card
and there you have connected your main monitors you said.

Its a good strategy to take an RME device as clock master and the main device which will get clock changes,
usually the device where your main outs are connected to. As it might be a PCIe card, it will also be the more
modern card compared to the old Multiface II. Maybe also the version of steadyclock is more modern on the
newer card (potentially already steadiclock v2).

So set the RME AES to clock source internal and
Multiface II: set clock to WC.
2 x Rosettas: set clock to WC

steadyclock v1, v2 and v3

The customer has a Multiface and a HDSPe AES in his computer. In his first post he refers to the AES as 'PCIe' card. See also the title of this thread.