Some not so good Vietnamese resturants use straight hoisin sauce for dipping. Not good for dipping rolls.
As for the dipping sauce, many people I know use pb/hoisin for a quick and easy way to make the sauce. My mom however makes it the old school way with a little beans in the mix.
I often wonder how the name of the salad roll got warped over time and various resturants. The roll you've made in Vietnamese is called goi cuon, litterally translated to salad roll. But I've heard them referred to as summer rolls, spring rolls and salad rolls. Too many darn names for the same thing I get confused.