The Ro.58 was a 2-seater Italian heavy fighter that was intended to replace the unsatisfactory single seat Ro,57. The Ro.58 used the latest German guns and engines giving the (single) prototype a much better performance than its predecessor. The design was plagued by development problems that meant the aircraft was not ready for production by the time of the Italian Armistice and so further work was impossible.
The spherical depression under the fuselage is for mounting the model on a 4.5mm BB.