Unfortunately, you can't reassign the function of the pitch bend wheel on the PSR-E433 itself.
Without using any additional equipment or software, probably the best you'll be able to do is use preset voices that have the rotary effect built in, tweak their sounds (e.g., the cutoff, resonance, reverb, chorus) as desired in the Function menu, save them to separate registrations, and "switch speed" by changing registrations.
That won't give you a smooth speeding-up or slowing-down transition, but you could see how it works out for you.
There are at least four voices you could try:
Voice 020 - Cool! Rotor Organ
Voice 345 - Rotary Organ
Voice 346 - Slow Rotary
Voice 347 - Fast Rotary
If you can use a computer, laptop, or tablet with your PSR-E433 while performing, there are apps that can convert one type of MIDI event into another, and you might be able to convert the Pitch Bend messages to some other type of message.
However, if you're able to use a computer, laptop, or tablet while performing, then the best solution would be to use an app that produces the rotary effect and applies it to the audio output of your PSR-E433 before passing it along to your external speakers.
A computer-free alternative might be to use an effects pedal that adds the rotary effect.
What sort of equipment setup and performance situation are you needing this for?
EDIT-- I forgot to say, gigging keyboardists tend to be highly critical of Yamaha's success at emulating the rotary speaker effect. The more expensive Yamaha models have an actual rotary effect that can be applied to any voices (not just organ voices) and then controlled as far as rotary speed and the depth of the effect, but the PSR-E433 doesn't have anything like that. But in any case, I've seen posts from people who gig with PSR-S and Tyros models who say that they run their sound through an effects pedal for a really good rotary effect.