Welcome to the Coffee Forums website. Do you roast the coffee that you sell, or does someone do it for you?
I usually prefer coffees that are medium roast, but it really depends on the coffee.
Even though I lean towards a medium roasted coffee, some coffees taste more flavorful at a lighter roast, and some taste better at a darker roast. There are so many factors. It's really difficult to select one particular level of roast for everything.
I prefer medium roasts, similar to a light roast you can often still taste some of the qualities of where the beans were grown and similar to a dark roast you get that bold, full flavor. Best of both worlds in my opinion!