Try using a manual impact driver. If you haven’t seen one, it’s a reversible tool that you hit with a hammer. The force of the blow drives the bit into the screw and at the same time it turns the bit to remove the frozen screw. You can pick one up at Autozone for about $12.00.
Thank you. I'll have to get a look at one to see if I can use it in the confined space I'm working in. I do have the option of removing the entire roller assembly from the machine, but I only want to do that as a last resort, as it's a bear to precisely align when re-installing.
Thanks for the tip!