It’s easier if you use a piping bag with a large tip on it to pipe the lemon curd into the rolls. If you don’t have a piping bag, you can up a zip-top bag and snip the end to pipe the lemon curd into the lemon curd rolls. You’ll need to work with it to get the lemon curd into the roll and not just on top. As well, you can spoon the lemon curd into the rolls. It may take a little working with the first time you do it. I found the piping bag and tip the easiest.