One's not satisfied with English in Roman assembly (6)
I believe the answer is:
moaner
'one's not satisfied' is the definition.
I can't judge whether this defines the answer.
'english in roman assembly' is the wordplay.
'english' becomes 'E' (abbreviation).
'in' indicates putting letters inside.
'assembly' indicates an anagram.
'roman' with letters rearranged gives 'moanr'.
'e' inserted within 'moanr' is 'MOANER'.
'with' is the link.
Can you help me to learn more?
(Other definitions for moaner that I've seen before include "Grouch" , "One who complains" , "Complainer" , "Grumbler" .)