Roaches do leave droppings, and where they tend to congregate, you will find a bunch of them. This is referred to as a “fecal focal point”… gross, I know. It is best to check areas that are near moisture, like the kitchens and bathrooms, as cockroaches need water to survive. Also, areas of clutter will provide protection against their natural predators. As always, it is not a bad idea to get a professional involved as they are trained in detection and identification.