Where does Rogatchover explain Oso v'Es Beno with a Kohenes using a bamah? Sefer ?
I believe you're referring to the Hashmatos on Tzofnas Pa'ane'ach (2), where he asks why the Mishnah in Bechoros stating that Oso v'Es Beno is permitted for people (and with animals it means a mother and daughter) could not be interpreted as referring to a Bamah, where a Kohenes and her daughter may bring Korbanos. He wants to infer from this that a Kohenes cannot serve at a Bamah.
Yoel Domb
What sefer are the Hashmatos on Tzofnas Pa'ane'ach in?
I searched all of the Hashmatos in various editions but it seems that this one (which I found in the Responsa project) is based on the 1979 edition of Tzofnas Pa'aneach which has organized Hashmatos. I think it is the edition on Hilchos Avodah.
Yoel Domb