Real Dictionary

roost
countable noun: A roost is a place where birds or bats rest or sleep.
verb: When birds or bats roost somewhere, they rest or sleep there.

roost in American English
a perch on which birds, esp. domestic fowls, can rest or sleep
to rest, sit, sleep, etc. on a perch
noun: a perch upon which birds or fowls rest at night

roost in British English
noun
noun: a place, perch, branch, etc, where birds, esp domestic fowl, rest or sleep