An Applescript that batch-copies the Song tag to the Movement tag
To delete the roman numerals, you can use the delRomNum() handler from this script:

--- this text as an example.
set movementText to "Telemann - Concerto in E minor: I. Andante
II. Allegro
III. Largo
IV. Allegro
etc."

set movementText to my delRomNum(movementText) -- delete roman numerals


on delRomNum(t) -- the perl command search and delete any roman numeral (must be a word followed by the period and a space character)
    do shell script "/usr/bin/perl -pe 's/\\b[IVXLCDM]+\\b. //g' &lt;&lt;&lt; " &amp; quoted form of t
end delRomNum


The result of the script is 


"Telemann - Concerto in E minor: Andante
Allegro
Largo
Allegro
etc."





Update:

If I understood correctly :

From each line in a string, the command must delete the characters
   from the beginning of the line through the first occurrence of (a
   roman numeral or an arabic numeral) followed by the period and a
   space character, so use this handler:

-- call it, like this --&gt; set movement of thisTrack to my delRomNum(name of thisTrack)
on delRomNum(t)
    (***  from  the contents of the 't' variable (the end of lines must be an Unix Line Endings), so the 'tr' command change the carriage returns (Mac Line Endings) to linefeed (Unix Line Endings)
    the 'perl' command delete the first character in each line through the first occurrence of a word  which contains (a roman numeral or a number) followed by the period and a space character ***)
    do shell script "tr '\\r' '\\n' &lt;&lt;&lt; " &amp; (quoted form of t) &amp; " | /usr/bin/perl -pe 's/^.*?\\b[IVXLCDM0-9]+\\b. //g'"
end delRomNum


Example: the script pass this string to the handler as parameter

Serenade for strings in C major, Op. 48 - I. Allegro
Serenade for strings in C major, Op. 48 - II. Adagio
Serenade for strings in C major, Op. 48 - III. Allegro moderato
Serenade for strings in C major, Op. 48 - 4. Allegro  Molto Appassionato
Serenade for strings in C major, Op. 48 - 5. Adagio - Allegro Molto
Serenade for strings in C major, Op. 48 - 6. Allegro moderato
VII. Adagio - Allegro Non Troppo
8. Allegro Ma Non Tanto
9. Largo
Adagio
etc.


The handler returns:

Allegro
Adagio
Allegro moderato
Allegro  Molto Appassionato
Adagio - Allegro Molto
Allegro moderato
Adagio - Allegro Non Troppo
Allegro Ma Non Tanto
Largo
Adagio
etc.