M-Spring Tension Roller with 1 Inch Steel Wheel for Sliding Screen Door.
Tension Roller consists of 1 inch steel ball bearing center groove wheel and heat treated, high tension, adjustable, steel spring.
This Roller is used by several patio door manufacturers.

Material: Steel
Roller Edge Type: Concave
Spring Type: M-Spring
Roller Width: 1/4 Inch
Roller Diameter: 1 Inch

Contents: 1 Roller Assembly
Priced and sold each.

Installation Note:
You will notice that the adjustment screw goes thru the spring and hits the top of roller.
If you remove the screw, the roller assembly will slide away from corner and allow you to drop the roller out the bottom, you may have to pry spring to get it out
Replace roller and reinstall screw for adjustment.