Don't forget that roaches fly. Personally, I chased one in our bedroom with a rolled up newsaper as it flew round. Wife was amused as I was doing a trampoline act on the bed stark naked.
We also had two in our flat in Kuwait and we lived on the 6th floor.
According to an article in Gulf Times some years ago, there are 3 types of roach in Qatar: American, European and the very quick Asian (aka Bombay runners). There are no arab cockroaches :)
If you find one, then look for its mate. They are invariably in pairs as they mate for life. The eggs are a bit like a wedge shaped apple pip.
We used a spray in Qatar that lasted for 6 months (sorry I cannot remember the name) but it smelled of oranges and it worked.
Anyone that has window type A/C units, you need to seal them as roaches love to get in through there.