It may be possible to get what you want for max 3 notes using Chord Note-Channel-Switcher by J, found here:
I haven’t come across any midi tools for round-robin, more’s the pity.
If you’re playing live then I don’t think there’s a way of doing what you need in Cubase. But for events already recorded you could create Logical Editor presets to apply round-robin channel changing. Check out the preset ‘Delete Each 5th Note’ because this can be modified to change the channel of every 4th note to ch4 for example, then a second preset to change every 3rd note (on channel 1) to ch3 and then every 2nd note (on ch1) to ch2. After running these 3 presets in that order once only you’d have channels changing 1/2/3/4 repeatedly through the midi notes in the event(s). You could write a macro to do it all in one go too!
Mike.