Just google 'Pepper Roaster' and you'll see companies that make them (I believe one of them is www.pepperroaster.com). People I know that do it get around the rules by not charging for the roasting - they sell the peppers and roast them for free, otherwise they would have to get permits for cooked food.

I done a diligent Google search and can't find a source for a drum type rotating pepper roaster. Anybody have any hints?

Oops! I'm sorry. Try googling 'Chile Roasters'. Most of the ones I've seen used in markets are large stainless steel drums with propane burners. All of them are very expensive (to me) so at home I just use the backyard grill. Mine don't come out as perfect as the tumbling roasters do but taste just as good. My friends have the smallest one offered. Keep in mind that these grills cook a lot of peppers at one time and you want to keep them operating as long as there is a crowd at your market, so think small and grow a lot of peppers.