Finishing pre-cooked prime rib, day-of?
Two stage cooking is generally not a safe practice unless the food comes to at least 130-140F during the first stage, held there an adequate amount of time to kill off bacteria, then is chilled quickly, and then reheated relatively quickly.  Commercial food service has a lot of fairly complex rules dealing with these sort of "pre-cooked" and reheated situations, because they are one of the places where it's most likely to cause foodborne illness.  

Since you likely wouldn't want to go to temperatures that high (and I don't blame you), I'd recommend cooking it all yourself at one time for safety reasons.

Also, aside from safety concerns, I agree with moscafj's comment: I'm not sure what the purpose would be here.  Is it to get some benefit from the "rotisserie"?  It's possible to get somewhat similar effects by roasting slowly (at low temperature) at home, even without a rotisserie.  

EDIT: Since the OP has identified the goal as decreasing cooking time, I agree with AMtwo that this process won't help.  I'd only add to AMtwo's answer that it might actively hurt the quality of the final result, as both the butcher's rotisserie and OP's relatively high-heat oven temperature will likely cook the outer layers of the meat further, while leaving the interior very rare.  Doing this twice will actually compound this problem, so if the goal is a rare roast (as I'm guessing from the target temperatures mentioned), this will actually result in a thicker layer of more "done" meat near the edges with more time to dry out.  Better to just cook it once.