Hanko question: Roman letters vs katakana for foreign names?

I had a question about hanko usage in Japan.

Do people ever use Roman letters for their hanko, or is it more standard to use katakana for foreign names?

Half my life I grew up and went to school in Japan, and for the past few years I’ve been using my parents’ hanko for some personal paperwork, and that one uses the Roman alphabet. Now I’m planning to make my own, but a friend told me that it should match the one I’ve been using before (like for bank stuff), otherwise it might cause issues or look suspicious.

I’m not sure how true that is. Does the design/name format of your hanko actually matter that much for consistency, especially with banks or official documents?

Also, side question since signatures are already used, why are hanko still required in so many cases? It feels a bit redundant.

Would appreciate any insight.