The opening spiel of the Great Movie Ride introduces your guide through the movies and sets your guide up as a very big fan of the films you're about to see. Within the spiel are two film industry references that have a literal and figurative meaning.
After the guests are seated and the proper warnings and instructions given by the host, he or she will say, "Ready when you are, C.B.". This is a a movie-making expression referring to famous movie director Cecil B. Demille. So why do the Cast Members say it?
The story goes that when Demille was directing one of his films he had three different cameramen shooting at different angles. The shot was a difficult one including a stampede of people rushing down a desert. Demille asks "Wow, did we get that shot? Who got it?" and the two camera men near him sadly were not ready and did not get the amazing shot. CB yells to a camera man way in the distance "Did you get the shot?" and the camera man says "Ready when you are, CB!". So the joke is that no one got this amazing shot and C.B. had to re-shoot the whole scene. Quite humorous, thus the line is used today at Great Movie Ride.
Right after that line is said by your guide, the ride vehicle will start moving forward and your guide says, "And we are rolling". This has a literal and figurative meaning as well. The literal is easy, the vehicle is literally moving forward but the phrase is also a movie making expression, meaning that the film in the camera is recording and they are recording it onto film. The rolling refers to the fact that old style film cameras use rollers to keep the film moving to record the images onto them.