Hi,
As the business partner is created in ECC first then replicated, the account group assigned in ECC is mapped to the classification in CRM via tcode PIDE (submenu "R/3->CRM: Assign Account Grp. to BP Classification"). You can check this in transaction PIDE in your ECC system. If the account group of the customer is mapped to the classfication "B", the BP replicated to CRM will be created under the classification IS_CUSTOMER which corresponds to the role "sold-to party" by default.
For your question, the "ship-to" role will not be added in CRM side for the same account. However, if you want the account group to be assigned as other roles such as CRM002 (ship-to party), you could use the event DE_EIOUT to enhance the user exit. In the note 914437, there is a sample user exit Z_PI_BP_ROLE_MAP_DE_EIOUT to achieve that.
Also, I created a SCN blog about how you could debug the customer delta load between ECC and CRM. Please refer to it if you are interested.
https://wiki.scn.sap.com/wiki/display/CRM/Debug+for+the+customer+delta+load+from+ECC+to+CRM
Thank you and best regards,
Julin Xin