One of the character items given to VOCALOID2 characters Rin and Len Kagamine. (also called Ren, due to the fact that Japanese people do not have a 'L' sound and pronounce the 'L' as a mix of a 'R' and an 'L' and has, by some western fans, been depicted as being spelled 'Ren' instead of the widely popular spelling of 'Len')
It is shown as a large, yellow road compactor (also known as a road roller) which the twins often use to run over the other VOCALOID's (most commonly KAITO), some pictures even show Rin running over Len. It's often pronounced by fans as 'rodo-rorra' when they prefer to stick to it's Japanese/VOCALOID prounciation.
Fan 1: Have you heard the VOCALOID song It's my Road Roller?
Fan 2: Yeah! It's really funny! I like that and Daughter of Evil's Road Roller!
Rin and Len: We're going to run you over with our Road Roller!