@garwoodredcap the issue here for me was that I was creating .sass files instead of .scss files.
As you can see on the source code
The rollup.js config is pretty straight foward!
It loads theme/variables.scss before everything else
Then all the scss files inside your root directory.
YOu can place the scss inside you components folder and reference them on scss with their selector name like
sg-login {
background-color: red
}