Roof Rats are also called black rats, and gets its name from its tendency to be found in the upper parts of buildings, are smaller than Norway rats, but cause similar issues. 

Pest Description:
 

• Color: Brown with black intermixed; Gray, white or black underside
• Legs: 4
• Shape: Long, thin bodied; pointed muzzle
• Size:  Head and body are 6 to 8 inches long, the tail is an additional 7 to 10 inches, and weighs 5 to 9 ounces
• Antennae: None
• Region: All
• Habits: Roof rats are primarily nocturnal. They are shy of new objects and changes in their environment, and will avoid them for days until they become accepted. These rats forage for food in groups of up to ten and like to return to the same food source time after time. These rats follow the same pathway between their nest and food. 
• Habitat: Roof rats live in colonies and prefer to nest in the upper parts of buildings, but can be found under, in and around structures. Outdoors, roof rats prefer to nest in trees, vegetation, and occasionally in burrows.
• Threats: Rats occasionally bite, and can introduce fleas into a home. Rats are vectors of leptospirosis; this disease is acquired by eating food and drinking water which are contaminated with infected rat urine. can cause damage to structures through their gnawing and eating.