 On the eastern boundary of the municipality, the Lützel drains into the river Birs, a significant tributary of the Rhine.Roggenburg encompasses the hamlets of Sägemühle (in the Lützel valley) and Neumühle (French Moulin-Neuf), which lies east of the Bösen, as well as numerous individual farmsteads.Roggenburg is in fact an exclave of the canton Basel-Country — it is only connected to the rest of the canton at a single point.