Roy was born on 21 October 1917 in Waco, Texas. His mother was Gabrella Sylvester Kent Flatt. His father was Roy Frederick Flatt.  

The Flatts trace their ancestry to Holland, where the name was van Vliet (or from the flatlands). Rumor has it that two Flatt brothers fought in the American Revolutionary War and were afterwards paid in land that contained a cave they called Flatt’s Cave. Years later it became a tourist attraction called Mammoth Cave in Kentucky.

Roy was a typical boy of his day, with a real zeal for life and adventure. He probably got into the typical kind of trouble for a boy of that time. He was always full of energy and daring.

Roy attended public schools in Waco, with an average scholastic record. He was very active in sports. He did not complete high school.