Voltage Regulator Module

My motorcycle idles bad every so often, other than a fuel problem, what about electrical?

This happens so infrequently, the dealer hasn't been able to nail it down. Should I go for a new ignition module, or voltage regulator? It seems like I have to keep rpm's up to keep the bike running. Then, after shutting it off and starting up later or the next day, bike runs fine.
bike is air-cooled
...and i don't suspect overheat

First, it would help if you have more info about your motorcycle.
Make, model, size engine, fuel injection?

But infrequent roughness does sound like fuel or carb to me. The dealer probably didn't spend much time troubleshooting if it ran fine when you brought it in, what I'd check would include:

Spark plugs for fouling, clean or replace if needed
Air cleaner
Drain gas completely and fill with fresh
Look for rust in the tank / install fuel filter
Run some good quality carb cleaner through it, maybe Seafoam

How to Rebuild an Alternator : How to Remove the Voltage Regulator from the Alternator