regular salt for the place of popcorn salt for the rolled buttercream..

I'm sure - popcorn is just a finer grade.

It might cause problems with your color, if you just add it in with the powdered sugar.

I would dissolve the salt in the liquid you're using, instead of just tossing it in. If you don't dissolve it first, the grains of salt will attract moisture after the bc is made, and can cause spots of lighter or darker color in the final product. This isn't always seen right away, but the spots develop over time as the cake sits for the first 24 hours or so.

Laura.

Wow, great advice, I had NO idea! Great question.....I'm sure I'd ask it at some point!

Which is why I don't use salt in my buttercream, especially since I use salted butter.

Wow !!! that explains why I had spots that I could not figure out why. Am always learning so much here at CC....

You can also grind regular salt more to make it a finer grade. Just use a mortar and pestal or a blender or a coffee grinder and grind until is very fine.