Main.min.css only changing when running grunt build

I have just setup the new roots starter theme on my localhost and am wondering what I am doing wrong in terms of my setup as every time I make a change only main.css is created.

What grunt commands should I run when developing locally as running grunt build every time would be time consuming.

Thanks for creating roots used it for several websites however just started building a new site using the latest version.

Solved looked around and found another post

Also see this post: Grunt won't create main.min.css

And this: Add x.min.css & x.min.script to watch