My recommendation would be to find out why cockroaches are attracted to that property:  "Cockroaches have simple needs: food, warmth, moisture and shelter. ...Cockroaches are attracted to food that has been left out on the counter, dirty dishes in the sink, and crumbs laying on the floor.

If done incorrectly it will trap moisture inside and hide the rot from view. 

Three years of being in the same place with the restroom having no ventilation is going to cause moisture to accumulate and peel paint.Thank you to everyone for the advice.

Inside the house the basement is finished and he found evidence there was standing water in the basement at one point, and verified moisture in the basement with his moisture meter.

Does the moisture in the air have a way to get out of the bathroom?

Have'nt had the moisture issue being trapped underneath as far as I know.Sunlight warping.

Now the moisture issue is something that need to be addressed.

The reason we put the bathroom fans in the bedrooms is to reduce moisture from when people breathe as they sleep and to reduce moisture that caused mold growth.

Whenever I deal with mold complaints, I ALWAYS use a moisture meter and photos.

Which we all know is easy to discolor from moisture, dirt, spilled drink even after deep cleaning the top.