All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
A group of the scholars are of the opinion that the waste (excrements) of living beings that do not have blood (in their bodies), like insects (amongst which are cockroaches), are pure, except for the cockroaches of sewage, because they are born from impurities and their excrements are impure.
Shams Ad-Deen ibn Qudaamah from the Hanbali school of jurisprudence, said in his book Ash-Sharh Al-Kabeer:
“Living beings that do not have blood are pure in all their body parts and their waste (excrements) [..] unless they are born out of impurity.” [End of quote]
Some jurists who are of the view that these excrement are impure, hold the view that little of it is excused because of the difficulty of avoiding them.
Secondly, If impurity touches the floor –whether it is the impurity of cockroaches or anything else –then you remove the impurity itself with a tissue and the like, and pour water over the place. There is no specific number of times that you are required to do that; rather, you pour water until the trace of impurity is removed, such as its color and smell.
If you predominantly believe that the impurity has disappeared, then this would be enough to rule the floor as pure, and it is not a condition (for its purity) that you must become certain of its purity, as stated by the jurists.
Allah knows best.