Where is your annotation stored? In the map or in a geodatabase?
IN the map: on the drawing toolbar, select Drawing >> Active annotation Group>> then select the one you wish to modify. Add your new labels.
In a geodatabase: Start an edit session on your annotation, and add your labels.
If your question is how to only label the new roads, do a join based on the road name. Then select by attribute, roadname1 = roadname2. Invert selection. label this selection.
Regards,
Jim