Boric acid is the only thing that really helped when I moved into a place with tons of roaches.
Another natural trap that was very effective with roaches was to put a little bit of beer and bread in a jar, and put a line of Vaseline on the inside of the jar so the roaches can't climb back out. They love beer and bread and will happily crawl into the jar to their own demise.
Of course, if you or a neighbor has dogs, make sure to do the jar trick with jars that the dogs can't mess with.
For ants, it can help to put a Vaseline border around any open water sources you can't get rid of (e.g., for us, this was our cat's water dish). They can't get through it and will have to seek alternative sources of H2O. This can also help if there are other spots you can't get to frequently (e.g., behind the fridge or stove, where some crumbs inevitably accumulate). Everything else natural that I tried (cinnamon, cayenne, vinegar, citrus, bay leaves, boric acid, etc.) was all completely ineffective on ants for me. I've heard these work for others though, so it was probably just that the particular species of ants I was trying to get rid of was cool with all of the above.