What is the difference between a cardiologist and a vascular surgeon? what are their roles?

Cardiologist: is an internist who specializes in heart disorders. Some cardiologists perform invasive procedures, such as angioplasty, stents, artificial valves, pacemakers, and other devices, but mainly in the heart. A peripheral vascular surgeon is a surgeon who specializes in surgical and procedural treatment of blood vessels, mainly arteries, away from the heart. Sometimes their expertise overlap.

Very different: Cardiologist = heart specialist. Vascular Surgeon = blood vessel specialist. Cardiologists are internal medicine doctors with additional heart training. Vascular surgeons are surgeons with additional surgical / medical training in blood vessel diseases of the arteries & veins. Cardiologist don't operate, but often do heart catheter procedures. Vascular surgeons do stents, PTA, & surgeries.