The joints in those rafters would perform nothing like modern end jointed lumber. Without plywood gussets on both sides or metal strapping around the joints, they would be too weak to be used as a rafter. The nails are in tension rather than shear, which makes them prone to pulling out.

I would definitely recommend gussets designed by an engineer. Although a decent carpenter with some glue and nails could easily add plywood to both sides and that would be strong enough.