Epson C13S990021 is a maintenance part for specific high-volume Epson WorkForce Pro printers, similar to the one you asked about previously. It is specifically designed for the optional, high-capacity paper feeding accessories.
 
This roller is responsible for picking up and feeding paper from the optional high-capacity paper trays or feeder units (trays that are added beyond the standard cassette).
It is a scheduled replacement part necessary to maintain proper paper handling, preventing jams and misfeeds in printers using multiple paper trays or high-capacity feeders.