Roaches can cause respiratory problems, but I'd take that over potential murder and rape.
Also, I would be very disappointed in my dogs if they didn't notice a person living in the attic. You can find a ball by scent--you'd better notice a person creeping around!
A person creeping around? That's just Paul, mate. You know Paul, he's been living in the attic for years. Stupid human, doesn't even recognize it's own flatmates.
I don't want random dildos hanging out in my house without my knowledge, friendly or not. At least with the roaches, I don't have to have a conversation.
I take your point, but the reasoning "this person has already demonstrated themselves willing, able, and motivated to breach a major social contract related to your safety; therefore I fear that they may try to breach more" is not unreasonable. The proportion of "home invaders who are also (willing to be) murderers" is gonna be way larger than the proportion of willing murderers among the general population.