Are you sure its rats, Ive had Flying Squirrels running in my ceilings
and walls as they go out at night, Mothballs in a sock with a string
attached for later retrieval, and a large bucket of amonia in my attic
made them leave, finding and sealing their holes fixed it. Gee Twice I
had them in the house and caught them alive, One just sat on my
fireplace 3ft away from me, they are tame and not scared of humans as
they never see us, they are nocturnal and common in many areas. It
could also be squirrels or chipmunks, Rats are usualy not in ceilings
running around, flying squirells are. You need to find their entrance,
seal it only after you evict them.