Hitting the same drum multiple times triggers different samples (which sound slightly different).
This is to avoid a machine gun effect (with the exact same sample on every drumhit it would sound artificial).
When you stop playback and play your track again from the start it could sound a little bit different because the first drumhit now does not start with the first round robin, but continues where the round robin counter has stopped.
These keyswitches let you manually reset the round robin counter, so that your track always sounds exactly the same (for example you could record these keyswitches at the beginning of your track, then the first drumhit would always playback the first round robin).
But to be honest if you don't have a problem, you can also just ignore these reset round robin keyswitches.
In principle you select the round robin with these keyswitches.
You can also activate "reset on transport" below the item I have marked in the picture above. Which will automatically reset the round robings each time you stop/start playback.
Sometimes you might find a specific round robin that just seems to fit (ie. the flam is slightly different, or the timing is just right, or the pitch was a perfect match for something else). This lets you pick that round robin so that it always on the note that follows it.