Which parts should I buy to replace these

Thank you for writing in your question. Looking at your top spring loaded roller assembly, take a look and see if our 23-196 will do the trick in a replacement. As for your bottom convex roller, our 23-199 comes to mind. However, you may also want to consider our 23-225, which has a ball bearing convex wheel, that provides a smoother glide. Review all the parts mentioned and let us know what you think. 

That is a good question. The door manufacturer use the top spring roller assembly, our 23-093, so the wheel will float as the door moves. They consider the bottom rollers with the adjusting screws the principle adjusting device for the door. I hope this helps answers your question. Please get back to us if any other questions come up. 

If you have a 23-246 top track and the top housing is similar to our 23-196, then I agree that our 23-222C should work for you. The 23-222B could work as well, but the 23-222C is a newer version and I have been told by other customers that it works better. It's ultimately up to you.