Roth is best known for his grotesque caricatures — typified by Rat Fink — depicting imaginative, outsized monstrosities driving representations of the hot rods he and his contemporaries built. Although Detroit native Stanley Mouse (Miller) is credited with creating the so-called "Monster Hot Rod" art form, Roth is accepted as the individual who popularized it. Roth is less well known for his innovative work in turning hot rodding from crude backyard engineering where performance was the bottom line into a refined artform where aesthetics were equally important, breaking new ground with Fibreglass bodywork.
In the 1960s, plastic models of many of Roth's cars, as well as models of Rat Fink and other whimsical creatures created by Roth, were marketed by the Revell model company.
Roth was active in the field of counterculture art and hot-rodding his entire adult life. At the time of his death in 2001, he was working on an innovative hot-rod project involving a compact car planned as a radical departure from the dominant "tuner" performance modification style. In his later years, Roth's telephone number was listed in the directory, and he encouraged fans to contact him: he was always generous with his time and enthusiasm.