As per HTTP Status Code 403 description:
The HTTP 403 Forbidden client error status response code indicates that the server understood the request but refuses to authorize it.
This status is similar to 401, but in this case, re-authenticating will make no difference. The access is permanently forbidden and tied to the application logic, such as insufficient rights to a resource.
So most probably the user which is successfully logged in doesn't have appropriate permissions to perform the action you're trying to implement. Make sure that you're using correct credentials and the user role is the one which can do the lookup of other roles.
If you're able to perform these steps successfully in the browser most probably JMeter sends something different, you need to compare the outgoing requests originated from JMeter and from the real browser, better using an external sniffer tool, the requests must be exactly the same (apart from dynamic parameters which needs to be correlated)
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