Both editors and viewers can set their preferences for receiving notifications. To change your preferences, click the person icon at the top of the screen (Settings) and select Your Settings from the dropdown. There will be a bell icon/Notifications option where you can update your preferences. By default, email alerts for comments is turned on for editors, and off for viewers. Notifications for roadmap changes is turned on and set to Weekly.
Additionally, you can choose which roadmaps to receive notifications for from your Notification Settings page. You can also choose which types of notifications you want to receive for each roadmap.