Thanks for the feedback!
For something that bills itself as "rhythm driven", this game is incredibly slow-paced.
Our understanding of "rhythm-driven" might be different here. For me, it is very different from "velocity-driven". Instead of just getting as fast from A to B as possible using your reflexes, you have to carefully proceed through the levels. Good observation of trap patterns, perfect timing and puzzle solving are key in Roll Playing Game's campaign.
That doesn't mean it has to be slow-paced, though: Level 1-2 is probably the slowest in the whole campaign, because you have to wait for the slow rotating laser beams to clear the path. I'm currently reworking the 2nd and 3rd level to make them more open and faster and provide shortcuts/alternate routes. 1-4 introduces timer buttons that require fast movement at certain sections in the levels. Evil balls and projectiles will hunt you down in later levels, too.
Also, as I know that many marble fans love speedrolling, there will also be a bunch of "Rush" levels (partly based on the campaign levels). These include a timer and highscore lists, you can challenge your friends to beat your score in a certain level etc. Add to that the community level support and there should be plenty of speedy content in the game.
Still, overcoming/solving rhythmic hazards and puzzles represents the core of the game and if one doesn't like that, he/she would probably be better off looking for different kind of game. Roll Playing Game goes more in the direction of Ballance/Switchball instead of Monkey Ball/Marble Blast.