Diet of rolls — add sandwiches from French (9)
I believe the answer is:
bundestag
'diet' is the definition.
(German parliament - diet can mean a parliament)
'rolls add sandwiches from french' is the wordplay.
'rolls' becomes 'buns' ('bun' can be a synonym of 'roll').
'add' becomes 'tag' (as in tagging something on).
'sandwiches' is an insertion indicator (goes on either side like a sandwich).
'from french' becomes 'de' ('from' in French).
'buns'+'tag'='bunstag'
'bunstag' placed around 'de' is 'BUNDESTAG'.
'of' is the link.
(Other definitions for bundestag that I've seen before include "German house" , "German diet" , "house in Germany" , "German parliament building" .)