Assign multiple business roles to user

CRM Web UI
You can assign all/single roles using SU01 parameter CRM_UI_PROFILE (give role name or * for all roles)

If you want to assign multiple (example: 3 roles), then use PPOMA_CRM
PPOMA_CRM.
Here, please create an position, then via the menu path Goto -> Detail object -> Enhanced object description, assign a UI profile to Business Role. Now all the users assigned to this position will take the UI profile. One user can be assigned to multiple positions, so you can give one user more than one UI profile.

Ref:
http://p0006br4.benxbrain.com/en/sap/transaction/PPOCA_CRM-How-do-I-add-more-than-one-UI-profile-.-thread-1-1845126.htm