gistfile1.cs

            var sourceStream = new PBFOsmStreamSource(
                new FileInfo(@"path\to\file.osm.pbf").OpenRead());
            
            var completeStreamSource = new OsmSimpleCompleteStreamSource(sourceStream);

            foreach(var osmGeoComplete in completeStreamSource)
            {
                if(osmGeoComplete.Type == Osm.CompleteOsmType.Way && 
                    osmGeoComplete.Tags != null && 
                    osmGeoComplete.Tags.ContainsKey("highway"))
                {
                    // do something with the road here.
                    // the nodes are actuall here, just extract their coordinates.
                    var completeWay = (osmGeoComplete as CompleteWay);

                    var coordinates = completeWay.GetCoordinates();
                }
            }

This uses a PBF source and wraps this source into a 'complete' stream. The complete stream composes ways and releations with the actual instances of the nodes and members.

Be careful when using this on a large file.