fwiw, i've personally never had any trouble with asio4all, across multiple machines, xp and 7, 32/64, multiple daws, multiple soundcards, i still use it with my alesis photon x25 and laptop as the alesis drivers suck(ed) big time, and i also use it without issue with the same laptop with a numark dj interface...
 
try with another daw or audio app that supports asio, see if it still buzzes, this will remove asio4all from the equation (or not)
 
good luck!

What I'm saying is why are you using ASIO4all as your timing master? Get rid of it and use the Roland's drivers. Until you do that there's no way your system will be working properly as it should. 
Lawp you are using asio4all because you have an interface that is well known to come with bad drivers, You say you don't have issues? I bet  you'd see how crippling it is if you switched to a proper interface with good drivers. I speak from experience..long time ago I was in the same boat. 

As others have said please get rid of ASIO4ALL.

If there is a buzz, what about a cord being bad?
 
And like the others suggest, try a different driver/DAW to make sure it's not a cord or something else.
 
As for ASIO4ALL, I have had mixed results with it. I tried it on this PC back when I still had a old dual core Penti in it. It was a hit and miss to get it to work.
 
Now I have an AMD 6core and am using the Realtec drivers in WDM/KS for now. I never use this PC for recording. Just playing around and testing mostly.

Well I also have a edirol ua-1000 and a esi waveterminal 192 m, can't say I've noticed... But you're correct in saying the alesis has crap drivers ;-)
"ymmv" of course

I use ASIO4ALL for several devices. It wins every time compare to all not native ASIO approaches with the same hardware.
 
But in case there is a working native ASIO driver, it should be used instead (as was mentioned several times already).
 
For ASIO4ALL: in case there are more then one audio device exists in the system, ASIO4ALL will by default connect to all of them and neither are going to work. You can disable not required devices in the ASIO4ALL settings (I do not mean SONAR settings), and do not forget to restart the driver/system after that change. Start with really big buffer, like 1024. From my experience ASIO4ALL can not go really low with USB devices.
 
For hardware: check that you do not have any USB hub / long cables between your interface and the computer. Start testing with all other USB devices (and hubs) disconnected. Try several ports before you come to any conclusion (depending from the system, different ports can even have different hardware on computer side and in all cases interrupts distribution makes some ports better then other).
 
With Latency Monitor check that you do not have something "heavy".
 
I could always get ASIO4ALL working ok, even on 10m long USB extender with hub and crappy interface. But I will not claim I could enjoy playing software synth throw such system
 

+1 for checking asio4all is only wrapping a single device

And, I use asio4all for "live " situations, never for recording

Well, I say "never "...

asio4all can be very polarizing on this forum.  those who hate it tell everyone to never use it under any circumstances and some will testify how well it has worked for them. I can't think of any reason to use asio4all if you already have a interface with decent drivers.  There are a few cheap interfaces that have drivers so poor  that it is a possibility, but if the interface is that bad, you may be better off using WDM.  With that said, asio4all has been a lifesaver when using laptops or underpowered computers without an interface.  CPU effecient programs like FL studio and Acid work on very modestly powered computers using asio4all. i know some of the resident tech snobs here claim it only hurts , but I have seen firsthand times when asio4all worked when all other methods failed misreably.  perhaps it is a mass delusion, but it a mass delusion that has allowed many people who were not in the position to upgrade computer and/or interface to use various audio software.  In fact at the studio i work at, we have two computers that have FL studio running with asio4all (fl studio actually gives option to install asio4all during install) and they work fine.  no clicks, pops or any other problems.   I wouldn't recommend it for programs like Sonar, Cubase, Pro Tools, but it can be useful for lightweight programs for people on budget.