HP LaserJet PRO M521 Repair Manua page 82

2.
Release two tabs, and then rotate the roller out and away from the product to remove it.
TIP:
It might be easier to release the tabs by using a small flat-tip screwdriver.
Figure 1-104
Remove the Tray 1 pickup roller (2 of 2)
72 Chapter 1 Removal and replacement ENWW