Hi Logan,
Good question. The updates section in the WordPress dashboard doesn’t have a link for changes like the one for plugin’s does. I’ve always found that perplexing since users routinely make changes to themes more than plugins.
What you can do is download the theme from our downloads section and open up the zip file there. Inside the folder that you extract you’ll find a change log that goes over changes made to each file since the last update.
The absolute best practice for updates is to use a staging site. That way you can test out theme and plugin updates without affecting your live site. Some hosts like WP Engine have that built into their feature set so you can easily set up a staging site whenever you need to.
For this most recent Grassroots update, not much changed. Here’s a copy of those:
12.19.2015 - version 1.2.2
* /layouts/hero-options.php -- removed navigation visited states
* style.css -- removed navigation visited states
* /includes/custom-css.php -- changed current page drop down hover cover to be more specific with visited pages.
Let me know if I can help,
Bill