I'm a little confused on what exactly your question is but I'll try.
Method 1 = find a RD you like, mute all but the drums, title the song, then save it. On play back you will only have the drums.
Method2 = loop within a RB - highlight the measure(s) you wanted repeated, click on the loop icon, then click on play and loop highlighted area.

I hope this covers your request and good luck.

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Why is it that doctors call what they do 'practice'?
If flying is so safe, why do they call the airport, the terminal?

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware