I have some information about this Johan Pabst and Johanne Christianne Romer (born 1780), particularly their Pabst descendants (they had 3 children who emmigrated to Australia in the 1840's). Zellerferfeld is a mining town which slowed greatly in the 1840's. This line of Pabst moved to Australia to mine there also. Please let me know if you are interested in any information concerning their descendants.
I have searched the church records in Zellerfeld and the only additional information about their ancestors I could find was the name of their fathers:- Heinrich Ernst Romer and Leopold Pabst. I am hoping a visit to the neighbouring Clausthal Village may deliver more information.