John Williams Joseph "Bunny" Roser (November 15, 1901 – May 6, 1979) nicknamed "Jack", was a professional baseball player.

He was an outfielder for one season (1923) with the Boston Braves.

For his career, he compiled a .239 batting average in 113 at-bats, with 16 runs batted in.

He was born in St. Louis, Missouri and died in Rocky Hill, Connecticut at the age of 77.

This biographical article relating to an American baseball outfielder born in the 1900s is a stub.