It starts on the northern end of the Boyle bypass, and runs on a relatively new bit of road to the town centre, where it rejoins the original route running south. There's a fairly uneventful run to Tulsk, where the road meets the N5 at a set of crossroads, then it keeps heading south towards Roscommon. There's a bypass with the town, and a brief multiplex with the N63.
After this, it runs to the west of Lough Ree, without ever getting quite close enough to enjoy views of the lake, before it ends at a grade separated junction with the N6 Athlone bypass. This section connects Roscommon, the only county town not on a National Primary route, to Dublin. It is decent S2 in flat countryside and has an AADT of about 7500 south of Roscommon.