In that case you could do it by just having 2 (or however many) ads for the adgroup (identical, but change the destination URLs) - set them to show evenly and robert's your mother's brother.
I don't know how this would go with the TOS though - you'd have to ask Google or read through them.
I also notice there is an adwords advisor here and perhaps he or she could shed light.
steverose, the precise answer to this question lies in the particulars.
My instinct, based on what you've said so far, is that it would probably be OK. But at the bottom line, this is exactly the sort of question that is sorted out on a case-by-case basis by the review team - when they have all of the details in front of them.
My best advice would be to create the Ad Group, and submit it for review. ;)
AWA
I have written laying it out and will wait for a reply.
It would be too much to create a rotator and involve others if I did not know it was OL -- though I could put the url in with just myself and one other and see what happens.
This could work as my response rate is excellent now.
If we get five of ten sharing the same rotator we can up responses radically and reduce costs for all concerned.
Win-win.
Cheers and thanks again, S