I can tell by the tone of your question that you are totally frustrated and upset by what has happened. German cockroaches can multiply so fast that in a matter of a few short months, their population can "explode". Getting control when the numbers of german roaches are in the thousands will take some time, but with a little persistance, patience and using the right products, you can get rid of them.
We have a complete page on how to get rid of german roaches here - http://www.epestsupply.com/cockroache...
I would start by using bait such as Maxforce Cockroach Bait Gel -
placed into the cabinets and wherever you are seeing the roaches. Use small pea size placements and put it into the corners of cabinets, dressers, baseboards, cracks and crevices. Keep replacing the bait as the roaches eat it. Baiting is by far the recommended treatment over spraying. Spraying to try to control a really heavy german cockroach population can be a futile attempt, you can't spray everything.
If you must spray something, then use Invader - This is what a lot of pest control companies use to kill cockroaches on contact. Works faster than RAID. It's a fantastic product. You can spray the roaches on contact, you can also drive them out of cracks and crevices. It comes with an injection tube that you place into cracks around cabinets, baseboards, etc.
It is almost imperative that you use an Insect Growth Regulator or Sterilizer called Gentrol Point Source - place this under sinks in the kitchen and bathroom. Gentrol will help to control the life cycle, and slow down the reproduction process. Basically it is birth control for german roaches.
Dusts such as Borid (boric acid) need to be applied inside of plumbing areas inside walls, electrical switch plates, behind the refrigerator, washing machine, dryer, dishwasher, etc. A light application is all that is needed. This is about the same as the amount of dust on furniture, a light coating is all that is necessary. Use a good duster such as the Eaton Duster to do this.
I know this is lengthy, but there really is no way to go about doing an easy treatment for German roaches. Most professional pest companies would charge a minimum of $200 just for the initial treatment, so by doing it yourself, you are saving the cost of time and labor. I would estimate the total time at about 6 hours, over a period of 3-4 treatments.
This is something you can do yourself, and this is how the pros would do it. Don't spray baseboards or cabinets with water based sprays. Use baits, dusts, Invader and Gentrol and you will get results. Hope this helps.