This is indeed the same Sieja family. Agnes Gajewski (age 19) married Adalbert Sieja (age 25) in the parish ofLegowo-Tarnowo in 1849. She came to the US bringing 2 of her children, Valentine aka William, and Marianna. She is traveling with her daughter, Catherine and son in law Thomas Guzdial on the ship Hevelius arriving in NY on 26 April 1880. She is on the 1880 BC census in West Bay City as Agnes "Scherr".
John Roznowski (senior)'s wife is given as Rosalia Davidowski in several of the BC marriage records.
Please feel free to email me directly if you have any questions. fran