If you do not have web console permissions to do so, but have the ability to activate a service account that has the viewer permissions or IAM permissons to list IAM roles in a given project, the following is how you can list the roles for a given user or service account.
gcloud projects get-iam-policy <gcp-project> \
--filter="bindings.members:<email-address>" \
--flatten="bindings[].members" --format="table(bindings.role)"