Contrary to what many people thing, rats/roaches do not affect people on lower floors more than higher floors, even for big highrise buildings. There is less of an issue in very new buildings, but anything older than about 5 years old is about the same.
I researched this about a year ago by looking at the Census NYC Housing and Vacancy Survey data.
I would also be cautious of buildings that are above restaurants.
NYC is now publishing its 311 complaints data online, which includes rat complaints, among many other things you may want to check:
https://nycopendata.socrata.com/
Rat complaints may also be handled by HPD, which you can see here:
https://hpdonline.hpdnyc.org/HPDonli...e_address.aspx
This website also includes data from the above two sources, and also seems to some additional information as well.
https://revaluate.com
Depending on what kind of building you are looking at, if it is a large rental building, it may also have reviews on:
http://www.yelp.com/
or
http://apartmentratings.com/