I think some of US Chief Justice Roberts speeches and interviews on CSPAN might be a good resource, for example Chief Justice Roberts Remarks at University of Minnesota Law School. The nice thing about listening on CSPAN is that there is a transcript divided by timestamps, so you can read as he is speaking. Justice Roberts speaks at a reasonable pace, his accent seems to me to be a fairly neutral general American accent, and he chooses words precisely. When he is giving a speech, his language is very formal. When he is talking conversationally, it's a little more informal, but he doesn't use a lot of slang or colloquialisms.
The topics he speaks about might be a little challenging. His recorded interviews are about US law, and often refer to legal precedents and concepts that are well-known among Americans interested in law, but others may not understand all the things he references. He doesn't use as many "academic" words as Jordan Peterson, but he does use longer sentences than many speakers and I have yet to catch him making a grammatical mistake (that doesn't mean he never has, it's just rare for him).