I keep finding dead orientals?

Hello, I recently moved into an apartment wich used to be a huge attic, and after a few weeks I started to get sightings of oriental roaches in my apartment. I contacted my landlord and she said it was new to her, it never occurred, which i thing it's a nasty lie, and I'll tell you why later. Anyway she was comprehensive and told me she'll contact an exterminator if the problem persisted. Anyway, I started getting to war with those nasty guys: sticky traps, gel baits, pesticide spray, silicone seal. After finding a couple stuck in traps in the next couple of weeks, I then started to find only dead ones. Anyway, outside of the apartment complex and even in the stairway of it, I saw a few live ones during nighttime. In the last couple of weeks I could only find 1 or 2 a week and they're always dead. Is it likely that my actions are taking effect or is it just a case? When i feel paranoid about them, such as when i find dead ones, I always get up at night, turn my flashlight on and check the kitchen and restroom but I can never see them.

Note, my attic apartment is connected by simple to a couple of rooms that maintained the original attic asset, so they're directly connected to the roof tiles without any concrete, is it possible that they come through there? Of course I can't seal the tiles, but i spray residual pesticide under the door every few days.