Fruit fly problems? Just take an old tupperware or jar, drill a few small holes in the lid, then put some apple cider vinegar in the bottom with just a drop of regular dish detergent. The apple cider scent attracts them and the detergent prevents them from escaping. Dump it, rinse it, and refill with ingredients as required.
We tried this and the fruit fly population diminished considerably in our home.
Roach or ant problems? Unless you have a serious infestation, just buy a container of boric acid powder and sprinkle it in all of those dark cracks and corners where they tend to hide and retreat to. It's more effective than a lot of the other pest control products. It is also cheaper and far less toxic for pets and small children.