Returning user roles in the Assertion

Hi,

 We are developing a SAML 2 service provider and we are proposing that IDP's return user's roles in the SAML <Assertion> as an attribute (within <AttributeStatement>) as part of authentication response itself.

I would like to know:

1) What is the best practice for sending user roles from IDP to SP.

2) What are some of the widely used approaches (if not best practice) for sending user roles from IDP to SP.

Thanks,

Vasu