roost vs settle down

roost is a noun but settle down is not a noun.

Word	Noun	Adjective	Verb	Adverb
roost	Yes	No	Yes	No
settle down	No	No	Yes	No

As verbs, settle down is a hypernym of roost; that is, settle down is a word with a broader meaning than roost:

roost: settle down or stay, as if on a roost
settle down: become settled or established and stable in one's residence or life style

Other hypernyms of roost include root, settle, steady down, take root.

roost (noun)	settle down (noun)
a perch on which domestic fowl rest or sleep
a shelter with perches for fowl or other birds

roost (verb)	settle down (verb)
settle down or stay, as if on a roost	become settled or established and stable in one's residence or life style
sit, as on a branch	become quiet or calm, especially after a state of agitation
	settle into a position, usually on a surface or ground