It looks like you will need to use:

• list_role_policies() to obtain the names of inline policies attached to the role
• get_role_policy() to retrieve inline policies
• list_attached_role_policies() to list managed policies that are attached to the role

Then create a new role and use:

• put_role_policy() to attach an inline policy
• attach_role_policy() to attach a managed policy

Thanks to @JohnRotenstein for pointing in the right direction. I came up with a Node.js script to automate the IAM role copy procedure.

Steps it performs along with AWS SDK APIs used:

1. Fetch the source role along with its trust relationship policy: getRole()
2. Fetch inline policies of the source role: listRolePolicies(), getRolePolicy()
3. Fetch managed policies of the source role (both AWS- and customer-created): listAttachedRolePolicies()
4. Create a new role copying over all relevant properties (including trust policy): createRole()
5. Add all inline policies found in the source role to the new role: putRolePolicy()
6. Attach all managed policies from the source role: attachRolePolicy()

The process is quite straightforward... The only interesting detail is steps 2 and 3 require recursive fetch to accommodate the fact that policies response can be paginated.

How to make a copy of AWS IAM role.

If Python is an option, perhaps boto3 can be helpful (AWS's SDK for Python)

Creating a role: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/iam.html#IAM.Client.create_role

Creating a policy: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/iam.html#IAM.Client.create_policy

More: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/iam.html#client https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/iam.html