All of the above...

According to posts on the Windows 10 forum, 10240 is the "RTM" version.

Until M$ releases it or says it.. It's just speculation right or wrong.

I have a PCR-500, which probably is the same as far as computer connection.  I have the 10240 Win 10 release and I'll give it a try later today and report back on how it does.  Everything else I've done with Win 10, in relation to recording works exactly as it does in Win 8.1. 
 
I've only used the PCR-500 on Win 7 and not on my 8.1 installation.  I don't do much MIDI and thus rarely use it.  Just bought it when Guitar Center was "blowing out" the discontinued line as I didn't have a MIDI keyboard.

Did you try to figure out what CadErik suggests in "hacking the driver file"?
 
CadErik: I took a look at the downloaded driver INF files and I didn't see anything in there that was "hackable" in terms of the OS version.  Can you clarify what you changed in which files to make this work? 

Take a look at the INF file(s), which are text files you can open in Notepad. Most likely you'll something in there that specifies acceptable versions of Windows or file dependencies. If the person who created the INF was diligent, he will have liberally commented it and it'll therefore be easy to figure out what's what.

Looking into the RDIF1027.INF I see this section:
 

;---------------------------------------------------------------;

[Manufacturer]
%MfgName%=Roland,NTamd64.6.2,NTamd64.7

;[ControlFlags]
;ExcludeFromSelect=*

[Roland]
;; Windows7 - Windows XP 64
;; not supported

[Roland.NTamd64.6.2]
;; Windows8
%RDID0027DeviceDesc%=RDID0027Install, USB\VID_0582&PID_0033 ; PCR

[Roland.NTamd64.7]
;; not supported

;===============================================================;

Looks like they actively are blocking installation on other versions of Windows.
I haven't got Win10 installed yet, so I can't play around with the file to see how to bypass it.
But maybe adding the line 
 
%RDID0027DeviceDesc%=RDID0027Install, USB\VID_0582&PID_0033 ; PCR

To:
[Roland.NTamd64.7]

Might work

The issue here with this particular driver is that the version 7 driver SHOULD have worked with 8 and the 8 driver should have worked with 8.1, but neither was true if I recall correctly.  There was a new release of the driver for 8.1.  So, I'm not quick to blame Windows 10 on this since 10 has done fine with so many other drivers, even some not meant for 8.1 or 8, but this one eludes it - and in my case where I really had the obvious notice of the issue is that their "application" that does the installation doesn't even recognize that the device is plugged in during the install.  It's not even one of those driver installs that just does a courtesy install of the INF for you  - it's an actual application that doesn't even recognize the plugged in device.  As such, I'm not even sure that an INF file change itself would necessarily fix this problem.
 
That said - I wish I could try to do this modification, but I have some things I want to work on and the last time I fooled with this, I had to completely rebuild my system to get going again.  I really need to install on a separate drive and try there.  Unfortunately, I prefer an SSD installation as I have now.  I have a spare mechanical drive around that I could do this with, but that would mean that I'd need to install the OS, test this, then do the OS upgrade on my SSD - too many installs for the amount of free time I have these days :)

Looks like I should have read everything before I posted the remark!

fireberd
My Frontier Tranzport, which only has Vista drivers, installs OK using the Vista compatibility mode.

Geez, I'd forgotten all about the Tranzport, which has been gathering dust since I was unable to get it to work under 8.1. Maybe there's hope I can once again be reunited with my beloved Tranzport.
 
But then, I seem to recall that you had it working under 8.1, too.
 

Roland and Windows 10 support info:
http://www.roland.com/support/support_news/250010
 

There's definitely an issue with the Steinberg elicense software and win 10. No output and it crashes any Sonar projects that use the bundled plug ins.

Here is the latest from Roland
 
http://www.roland.com/support/support_news/250024

I put Win10 on my Surface Pro 3 last night - a painless upgrade.  I thought to try to install the pcr-800 drivers here on this Surface and (as expected) are still not working.  This is not my normal music computer, so it's a good place to prove the viability of them and then upgrade the music machine.
 
From the Roland news pages, it looks like there are plans to support 10 for devices that support 8.1, so I'm hoping that happens for this kb. 
 
BitFlipper - My Tranzport still works under Win8.1 - just have to run the driver installer in compatibility mode for Windows 7 and it runs right off.  Hope you get reunited!

Grrr....this is news since last night, as far as what I saw anyway.  That is really uncool - especially for a device that it seems would be a no-brainer to change the drive for.  Am I missing something here?  Dang- hope someone is able to come up with a driver hack.  Can't afford to replace the kb, it still works, does everything the Axxx series does, etc.  Not that HAVE to upgrade to Win10 right now, but grrr....