Charles-Philippe Lariviere painted the portrait now hanging in the Palace of Versailles. Rochambeau is depicted in full military dress, the way commanders of his era were depicted when the portrait was commissioned to commemorate their achievements. He has the expression of someone who has made a significant number of decisions under pressure and considers this a normal condition.
Rochambeau commanded the French Expeditionary Force that crossed the Atlantic in 1780 to support George Washington's Continental Army. The decisive campaign was Yorktown in 1781, where French and American forces combined to trap Cornwallis's British army on the Virginia peninsula. The surrender at Yorktown effectively ended the Revolutionary War. Rochambeau's strategic contributions to that campaign were substantial and not always publicly credited.
His name entered the lexicon of Rock Paper Scissors through ultimate frisbee, of all things. The ultimate community, sometime in the 1970s or 1980s, adopted "rochambeau" as a verb meaning to play RPS to settle disputes. The exact origin of this association is unclear. The game had been called "roshambo" in various American contexts since at least the 1930s, and "rochambeau" appears to be a more formal spelling of the same word, which may derive from his name through some chain of cultural transmission that historians haven't fully reconstructed.
What's certain is that a French count who commanded armies on two continents is now primarily known in casual American English as a synonym for throwing rock, paper, or scissors. Rochambeau's actual military career was exceptional. His posthumous RPS career is also exceptional, in a different direction.
The WRPSA art series includes him because his name is the game's most common colloquial American synonym, and because the portrait in Versailles shows a man who looks like he would win most of the bracket he was entered into.