finally I got it!!! ..helped by KPA support (thanks Hans 
) I finally succeeded in reamping in Studio One with Octa capture and KPA via SPIDF.. I´ve decided to public this little step by step tutorial in order to help others which have the same problems I had with understanding this topic.. maybe this could help also others who are using other DAWs and audio interfaces.. please, let me know if following these steps you are able to reamp with Roland Octa capture, Studio One via SPIDF (or other gear) excuse my english if not correct.. I would be happy if this will be of any help to anyone..
1. first make sure that the DIGITAL parameter in the Octa capture SYSTEM menu is set to AUTO
2. connect the SPDIF input of the Profiler to the SPDIF output of the Octa capture using a coaxial cable
3. connect the Profiler SPDIF output with the SPDIF input of the Octa capture using a coaxial cable
4. make sure that you are running your session at 44,1 khz and that the Octa capture is set to be the sync slave - do this by opening the surface control of Octa capture on your PC.. down on this surface you see: icons - octa capture – sample rate 44,1 kHz and clock.. CLOCK set as EXTERNAL
5. press and hold MASTER button on KPA, on page 1/5 in SPIDF output - select an appropriate output source - the most flexible one is the Git/Stack option which will output the stack signal without any of the post amp effects on one channel of the stereo SPDIF signal and the dry unaffected DI signal of the guitar on the other channel. This will allow you to record a reference track with the amp sound and a dry track for reamping purposes simultaneously.
6. press and hold INPUT button on KPA and set input source as FRONT INPUT
7. in Studio one create 2 mono tracks - name them DRY and WET - set input of the DRY track to the channel 9 and of the WET track to the channel 10 in Studio One - according to the Octa Capture manual the SPDIF is preassigned to outputs and inputs 9 and 10. (I prefer to rename these inputs as dry and wet also in Studio One´s Audio I/O set up section)
8. PAN DRY track completely LEFT – PAN WET track completely RIGHT! - now you should hear the dry signal from your left monitor and wet from your right monitor
9. enable DRY and WET tracks in Studio One for RECORDING - choose the rig for your WET track – press record button in Studio One and play your guitar. After you recorded your take mute the WET track with the stack sound!
10. create a new track in Studio One – name it for instance WET 02 and set the input of this WET track to channel 10 (WET) - do not forget to PAN track WET 02 completely RIGHT!
11. disable from recording the first WET track you recorded before, keep it muted
12. disable your DRY track from recording
13. press and hold INPUT button on KPA and select SPDIF Reamp as the Input source
14. be sure that outputs in Studio One are set to the channels 9-10
15. enable recording on the new WET 02 track - now when you playback recorded dry track you can hear the reamped sound of the rig you choosed for reamping..
16. adjust the Reamp Sens in the Profiler so it will match the level coming from your computer since that is probably much different from the signal that was coming from your guitar into the front input of the profiler (I prefer to loop some riff and while playbacking it I try various rigs till I find the one I like the most, the sound is changing instantly..)
17. when the appropriate rig found - RECORD - playback the already recorded track and record the new one at the same time. Repeat this process until you have a reamped track that you are happy with.
This process of reamping I find very useful not only for recording purposes but also when you need to find and tweak your sound among hundreds of sounds avaliable..
simply record your riff, loop it and reamp (instantly tweak parameters) till you find the sound of your dreams.. doing so, having your hands free, you can be concentrated on creating the sound, on changing parameters instead of on playing the guitar... I find this approach fantastic! 
ROCK ON!!!