Born in 1947 to a working-class family in Woodlyn, Delaware County, Pennsylvania, Trosley was fascinated by cars and drawing from early childhood.
He received formal art training through his teens at the insistence of his fourth grade teacher.
In 1973, Trosley set out on his own as a freelance cartoonist, and soon after, he was hired by CARtoons as a regular contributor.
Trosley is the creator of Krass & Bernie, a comic strip which ran continuously in CARtoons from 1975 until that magazine's last issue in August 1991.
Trosley also produced many other features for CARtoons, including a regular "How To Draw Cars" instructional series.