This is not made with puff pastry as usual sausage roll in UK, this is a bread roll. In Japanese bakery, there are many different type of savory bun/roll type bread, like this one.
I am a semi-vegetarian, a pescetarian to be precise, and I don’t eat meat (but eat fish). So I used vegetarian frankfurters for this bread. Soft white bread with a bit of brown mixed in, a touch of mustard inside, and Japanese mayo on top. Great for snack or lunch, and my boys loved it.