Here are some randomly selected joke topics beginning with the letter 'R'
Rock
What do you call a rock group with Mozart, Bach, Beethoven, Handel, and Chopin?
The Decomposers.
Roller skates
What is black and white and has sixteen wheels?
A zebra on roller skates.
Rockets
What goes up when you count down?
A rocket.
Roller skates
What is fat and jolly and runs around on eight wheels?
Father Christmas on roller skates.
Robinson Crusoe
He's leaving Friday.
Who is?
Robinson Crusoe.