Did the roll clearly propel the boat?
Was there any other reason for the crew's movement?
Was the roll associated with anything else : wave, wash, gust 

I had a similar incident in an SB20 event. Every so often, a crew would stand up, let the boat heel and then bring the boat back up to normal sailing angle.
We penalised on the 3rd time.

Hi David
I personally would not consider single actions that were 5 minutes apart and at different places down the leg to be repeated more than once in the same area of the leg. I therefore would not yellow flag such actions unless any one of them individually broke Rule 42. (But I would flag any one of them if I considered that they contravened BASIC 4 or ROCK 5).

Thanks Gordon, in answer to your questions:
The rolls did not clearly propel the boat.
There was no other reason for the crew movement.
No wash or waves, just flat water and less than 5kts of wind.

Thanks Graham, in the conditions described how close in time or distance after the first roll would the second roll need to be repeated for you to give a yellow flag penalty?

David, if you didn't see the boat propelled as a result of the crew's movement, the point of 42 is to capture artificially created propulsion. If you didn't see propulsion, then it looks like they didn't break 42.1. Could they have moved with these 5 minute intervals to  "perform other acts of seamanship, but shall not otherwise move their bodies to propel the boat". E,g. They moved to get a better view of their course? e,g. a look under a boom or around the mast etc. to re-check their course to the next mark?

That is harder to say David. If the second roll were within say 30 seconds (and even more so if there was a third roll within 30 seconds of that) then I might well decide that the rolling was repeated. If there hasn't been a second roll within a minute of seeing the first one then I would normally stop watching that boat and watch others instead (not good to get fixated on one boat). If I subsequently saw the same boat do another single roll then I wouldn't immediately consider that to be repeated rolling (i.e. rocking), but I might spend rather longer watching that boat to see how frequently there were doing such rolls. 'Fraid I can't say definitively how frequently they would have to be doing them for me to consider it to be rocking. Rightly or wrongly, I suspect my tolerance would also depend upon how aggressively they were rolling the boat i.e. how close I thought they were to breaching BASIC 4.

Repeated vs Periodic? If repeated is consecutive and periodic is 5 minutes apart then the time separation might imply periodic singular motions/rolling, and not consecutive repeated motions/rolling. Otherwise, if unclear,  amend the rule to define “two or more consecutive rolls” as “repeated”?