The bike is a Rondine but it is officially a CNA Rondine of 1935.
Count Bonmartini started out with GRB (Gianini, Remor, Bonmartini) in 1924. This company engineered the first 4 cylinder OHC motors. In 1927 he formed a company called OPRA (Officina Precisione Romana Automobili) which further developed these engines in race bikes with Piero Taruffi riding. In 1929 the race bike projects started to fade out.
In 1933 Bonmartini started an aircraft company called CNA (Compagnia Nazionale Aeronautica). Maintaining his interest in racing motorcycles CNA developed a 4 cylinder race bike in 1933. The engine was loosely based on the OPRA projects but was an entirely new engine and bike. It was first tested in 1934 and was named Rondine (Swallow) by Count Bonmartini. The bike debuted on the racetrack in 1935.
At the end of a fairly successful season Count Bonmartini decided to retire and sold the company to Caproni (an aircraft manufacturer). Caproni elected to sell the race bike program to a gentleman by the name of Guiseppe Gilera.
If only you had typed in CNA. The OPRA racers were not called Rondine and were a different (but similar) engine and a quite different chassis. You had everything else pretty much square on! I knew you had the answer there because it is in one of the provided links!