Steve Ritchie said in an interview that Rollergames was originally going to be High Speed 2, but that they changed the theme halfway through development when they got the Rollergames license. The "figure 8" light design from Rollergames was originally used on the High Speed prototype and was then resurrected for what was *going* to be High Speed 2, but ended up staying in the Rollergames playfield design.
I have both machines and personally can play Rollergames for longer than I can play High Speed (possibly because of the hypnotic music), but High Speed is great in its own ways and is a game that you can really get into the zone with.