As nouns the difference between carouser and arouser
is that carouser is a person who carouses; a reveller while arouser is someone or something that arouses.
carouser
English
Noun
(
en noun)
A person who carouses; a reveller
* 1836 Thomas Frognall Dibdin - Reminiscences of a Literary Life
- He was in the habit of receiving . . . from some hoary headed sage who had been a carouser at the “merrie court” of James V. of Scotland.