Hi Sunder
It is quite simple just goto table AGR_1251 and put only these 50 roles .You will get all the auth objects with values for these roles export it into a excel .Now in the excel delete everything except the auth object with values columns.Now add in another column auth objects and values of your new role.Now do a vlookup and you will get your difference if any.
Hope this helps
Regards
Pradeep