Faster still to avoid the uc entirely? Just double the hash:

   state %rtoa = (
       M=>1000, D=>500, C=>100, L=>50, X=>10, V=>5, I=>1, 
       m=>1000, d=>500, c=>100, l=>50, x=>10, v=>5, i=>1, );
[download]

A quick test shows it's not significantly different - just feels better. :-)