What can I legally do if I have roach in my food?

I ordered 3 chili cheese burritos l. I also got 3 sides of cheese sauce and I got mild sauce. I always open them and put cheese and mild sauce inside them. I did the first one. It looked fine. But I went to open the second one and there's what looks like a big roach. Looks like someone purposely placed it there. I'm sure they have cameras. I would be willing to take a polygraph to prove I'm telling the truth. I called talked to the manager and he listened. Then he asked me if I want to talk to my assistant manager. He can handle it. So the assistant got on the phone and then told us to bring it back tomorrow. I then got upset because that was sick and nasty. Plus I hadn't ate all day and was so ready to eat and go to bed. It was around 11 PM. went up there around 11:50. The assistant started to ask what he could get for us. The manager said just a minute guys. Then he came up. I showed him and explained what happened. He then said uh I would've noticed something like that. I said I found this in your food. He said ok but I would've noticed something like that. He kept looking towards the assistant manager. He then said they both made it. Not sure how that works. But I'm pretty sure they put it in there as some sick joke thinking no one would open it. What do I do?