German Russians 1860s

I have spent many years trying to locate the family of my g.grandfather's parents. It has been a frustrating journey. This is what I know, my g.grandfather's name was Johan Wuest Sr., he was married to Barbara Heil, they had 15 children, married somewhere near Rohrbach, So. Russia somewhere in 1880-1881. They had 3 children born in Russia before they came to the US in 1885, they came to Menno, SD, they founded the town of Heil, Grant cty, ND, along with my g.grandmother, Barbara Heil and some of her siblings and her Father, Georg Peter Heil. My g.grandfather Johan Wuest SR. was born 10/09/1861 around or in Rohrbach Russia. There have been many rumors that he might have been adopted at the age of 8, due to the death of his parents, but I have been unable to confirm this. I have also found the spelling of his name to be wiest, wust, hust in later records. So I guess I am hoping someone out there has some more information they can share with me and maybe break the mystery of where he was in Russia and maybe a bible to help with his family. I have asked and searched the children but so far no one is able to say what happened to the family (Wuest) Bible and I know my grandfather John Wuest Jr. didn't end up with it.