Only admin users have access to all rosters. If you're a teacher, you will need to ask an admin or the teacher that created the roster to share the roster with you.
STEP 1
Click Setup

STEP 2
Choose Rosters

STEPS 3 & 4
Click "My Rosters" and select "All Rosters"

STEP 5
Click the "Share this roster" button

STEPS 6 & 7
Choose Yourself and Any Other Admins or Teachers to Share the Roster with and Save

You'll then see the roster in your "Rosters" list on the Roster Picker!
