Gaston Gerosa competed as an amateur from 1943-56, mainly in his native Switzerland in track events. Four times he was on a winning pursuit team in the Swiss Championships – 1945 and 1948-50. He also competed in the sprint, placing second in 1950 in the Swiss Championships, and fourth in 1948. He represented the An der Sihl Velo Club in 1945 and later moved to the Radfahrer Verein Höngg club.
|1948 Summer||24||London||Cycling||Men's Team Pursuit, 4,000 metres||Switzerland||SUI||5T|
|1948 Summer||24||London||Cycling||Switzerland||SUI||Quarter-Finals||Heat One||2||5:09.2|
|1948 Summer||24||London||Cycling||Switzerland||SUI||Round One||Heat Three||1||QU||5:13.8|