Follow below steps to set list view as the default view:
- Go to SharePoint list & open "Rooster" view
- Click on Switch view options dropdown at the top right corner.
- Select Set current view as default.

Solution 2 - From classic view settings:
- Click on Switch view options dropdown at the top right corner.
- Select Edit current view.
- Check Make this the default view checkbox
- Click OK

Note:
You can only make the public view as the default view. If your view is private view, this will not work.
How to check the current default view:
- Go to your list
- Click on Settings (Gear) icon at the top right corner
- Click on List settings
- On list settings page, scroll down to the Views section
- Under Views section, you can see the current default view like below:
