What material should I use to seal door moldings, small holes between walls and floors to prevent roaches?
Just get a quality silicone caulk and go through the house caulking every opening. Get one that's paintable. They also come in a variety of colors so you might not have to paint over them. This type of caulk is water proof so if it comes in contact with moisture, you'll be ok. This will work on just about every surface there is. It also comes in tubes so you might not need a gun. The guns are inexpensive and you can get all this stuff at your home store. Good luck.