Do you have any additional information about Schnede? The only locality I can identify is a manor north of Salzhausen in Lower Saxony which in the 18th century would have been in the Kingdom of Hannover. You most likely will not find anything under the name John Root in Germany. John would be Johann, Johannes, or Hans, the last name could be anything from "sounds like ..." to a translation (root in German is Wurzel). I don't think he was a member of the Brethren from the get go, The Schwarzenau Brethren, who later renamed themselves as German Baptist Brethren, had already left Germany by 1733. But he may have found this group through his association with Quakers as they share some common beliefs.