How can you tell if you have roaches?

Hello! I’d love some serious help. Its just me and i have no idea what I’m doing.

I moved into my new home in October. The lady who lived here wasn’t that clean, and I was terrified she had roaches, so i cleaned everything when i moved in as best as I can and didn’t see any signs. one of my biggest fears is having roaches (I have OCD). I haven’t seen any so far until yesterday. I saw a big brown roach on my kitchen wall, during the day. It scurried away before i could kill it and have no idea where it went. I called a pest control guy right away and he came out this morning. At first he tried to say it wasn’t a roach from the picture, but it definitely is and eventually said it most likely was. He looked around my kitchen, and said he doesn’t see any signs of roaches. He sprayed some stuff around my baseboards of my whole house and said it was probably just a “fluke” and that i should be fine. My question is, how screwed am i? Do i definitely have roaches? How can I tell? My kitchen isn’t that big and I use my oven often. I also clean all the time. Is it possible that it was just a fluke? How can i look for them? Any help would be much appreciated.