You can assign multiple roles to a user by checking multiple role values in the Edit Roles section under User Administration . Follow the steps below to add multiple roles for a user:
1. Go to Account -> User Administration
2. Click on the desired user's name
3. Click on the Edit Roles button
4. Select the module to provide additional role access.
5. Then check each additional role for the user, Administrator, Manager, Representative or Custom Role.
6. Next, set the default login role for the user.

After login to switch roles go to Preferences -> Security -> Switch Roles
1. Select the role and click on the Switch button.
2. The application will now be presented for the user in the new role.