Roaches like to feed where they are nesting and you will be able to see their droppings when populations build up. Although there are many baits being produced, Avert Gel is also one of the bait I use. Use the gel where you need precise applications. Remember, the places to treat are primarily around and under water sources and in the farthest corners you can reach. You may see dark runs, or places where roach spittle has been excreted in corners and where roach droppings accumulate.
Roaches seem to defecate in the same areas and are attracted to such accumulations.
Take your Bulb Duster and Delta Dust and apply in the wall voids on the perimeter of your home. Get to these areas by removing the electrical outlets and penetrate into the void with a puff or two of the fine Delta Dust . Also apply around the opening in your wall where the pipe comes through, and then seal it with caulk. That will permanently rid that opening as a source of entry for roaches. These products will lure roaches and once they feed, they will die.