What is rock opera?

Wikipedia defines a rock opera as a work of rock music that presents a storyline told over multiple parts, songs or sections in the manner of opera.
The LA rock opera company virtually copies that definition: a work of rock music that presents a dramatic story told over multiple songs in the traditional manner of opera.

The free dictionary defines it as albums of rock music that aspired to the status of art; first appeared in the 1960s. Are we not blessed that we do not have to rely on dictionaries any more!
Here are just some of my observations.
Looking at videos of rock operas online, it becomes clear that the format of rock opera is fairly open ended. Some rock operas have impressive backdrops and sets. Others have none at all. Some rock operas have impressive choreography. Others have none. While many rock operas are close to musical theatre with actors acting and the band hidden in the pit (e.g. Jesus Christ Superstar), in some rock operas, the band forms an intergral part of the show (e.g. Tommy, The wall).
The one common aspect of rock opera is that all the songs together makes up a central theme or story, and usually must be performed in a specific order. There are some rock operas out there where the songs are more closely related to the directors favorites playlist, but I would place those rather in the category of juke box musicals. Most successful rock operas consist of songs written specifically for the show.