Anybody could explain why the operation assume-role-with-saml needs some parameters that are already in the saml-assertion such as role-arn and principal-arn?
After some research I'm able to answer. I was asking why send the --role-arn parameter if it is already in the saml assertion. In fact the saml assertion can have more than one role so in the api request is necessary to identify which role should be assumed. I found the answer in this link