As nouns the difference between roo and coo
is that
roo is peace; quietness while
coo is the murmuring sound made by a dove or pigeon.
As a verb coo is
to make a soft murmuring sound, as a pigeon.
As an adjective coo is
cool.
As an interjection coo is
expression of fright, surprise, approval, etc.
As an initialism COO is
chief operating officer.