If you don't have pets, sprinkle some boric acid around to where you are seeing them. (I would probably spread it around every opening I could find, including the sink). Let it sit for at least 2-3 days, a week would be much better, then vacuum it up and wipe everything away.
It may take a few weeks, but it WILL get rid of spiders, ants, roaches and other crawling insects. It will not do anything for flying ones.
We rented a house when we were in college and it was INFESTED with roaches. If you went to the kitchen at night and turned on the light, you could hear them scatter. It was gross! An agriculture professor told us about this trick and it worked miraculously.
