A Bay Ridge pharmacist embroiled in a public steroid investigation appears to have killed himself. John Rossi was found last night in the office above the pharmacy, with a fatal gunshot wound to his head and a pistol in his hand. Bottles of Johnnie Walker whiskey, Valium, and Coca-Cola were on the desk in front of his body; another bullet slug was found in the office, causing a police source to tell the Daily News,......