Replacement roller assembly

My sliding door is 30 years old and I need a new roller assembly. The pictures above were roller I bought at Ace Hardware and they ran out. I need one more to complete job. Notice the screw that is used doesn't have a nut on end but rather the screw goes through a housing neck with does not require it to need a nut. A nut makes it impossible to assemble once in place. All I can find in the hardware store is a nut style. I also included a picture of the packaging for the roller assembly that is correct fit for my door. thank you for your help. lynn