If you are going to customize or develop functionalities in SAP CRM 7.0 system, and you want to have access to different Web UI Roles, for sure you will want to choose them at least at logon. So, there is un easy solution for this - set user parameter CRM_UI_PROFILE to *. If you don't know how to do this: start transition SU2 and create parameter as mentioned. After this you can start SAP CRM Web UI with transaction CRM_UI. After logon you will have un option to select your profile.

Set CRM User parameter for choosing WebUI Profiles