gistfile1.cs

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

            foreach(var osmGeo in sourceStream)
            {
                if(osmGeo.Type == Osm.OsmGeoType.Way &&
                    osmGeo.Tags != null && 
                    osmGeo.Tags.ContainsKey("highway"))
                {
                    // do something with the road here.
                    // the nodes are just ids. save them from the stream first and get their coordinates.
                    var way = (osmGeo as Way);
                }
            }