As adjectives the difference between cloudy and roily
is that cloudy is covered with or characterised by clouds; overcast while roily is (of water) muddy, cloudy (having lots of sediment).
cloudy
English
Adjective
(er)
Covered with or characterised by clouds; overcast.
Not transparent or clear.
Uncertain; unclear.
roily
English
Adjective
(er)
(of water) muddy, cloudy (having lots of sediment)
turbulent