It is common in group practice. All the OBs/midwifes will get to know you during pregnancy. And the one on call will be help you in delivery. There should not be any resident seeing you independently. But you shall call to confirm.
Rotation. I am old also. It is said the insurance for OB in NJ is expensive, most clinic here are group. So far I met 3 of them from 5. They are all good. But I like one most , so I am trying to keep seeing him. You can ask the nurse evry time setting your appointment. For the first one as new patient, you have no choice.