The camera that I bought is the Amcrest ProHD 1080P. It's an indoor model, rather than outdoor, so has the ability for remotely panning and tilting by the viewer. I put it up in the attic and observed all kinds of antic by these cunning roof rats.
Before buying I researched on the Web, and some other brands are a bit cheaper, but have buggy software. The one I bought was rated a lot higher, and I have had no problem so far. I programmed it to only capture video when there's detected motion, and to store it on my network hard disk for my examination later. I can use my computer to access it through the home WiFi network and to see through the camera in real-time too. I have not used some of its capabilities like e-mailing, or viewing through a smart phone, or viewing from outside of the home network.
The camera is infrared, so no light is needed. However, the video then becomes black-and-white, and loses the sharpness of the daylight color mode. It is enough to see what the rats are up to, and how many of them are around. Rats do not have infrared vision, so it is amazing to see how they maneuver around using mostly their extremely sense of smell, and their whiskers for close sensing like a blind person using a cane.
I thought that the design was superior to the conventional snap trap. With the old trap, a smaller rat may mount the trap backwards, and the snap bar would just fly over its head. It is also perilous for the person setting the trap to avoid getting fingers smashed. This Tomcat trap is set by pressing a lever in the back. If you hold that lever down with one hand or a foot while baiting to keep the jaw opened, it should be safe. Also, the bait should be small and put deep in the well. That requires the rat to step on the tongue in order to reach in.
Well, you may have some neighbors like mine who have fruit trees, or leave out food for their cats or dogs. These roof rats can travel up to 300 ft from where they live to where they feed. The most we can do is to make sure they do not enter your attic or garage. This requires vigilance.
What is infuriating for me is that the roof of my 2-story home is too complex and has too many nooks and crannies. The tile roof also does not help, as the tiles have hollows and do not lay flat like shingles to make inspection easy.
If I end up giving up and calling in a pest control guy or a contractor, at least I know what I have done, and the guy must know to do more than that. It's part of self-education now.