Yes, gastroparesis can be caused by autoimmune diseases. Actually, autoimmune diseases can cause peripheral neuropathy and kill off your autonomic nerves, which control food moving through your stomach. Here's the MedHelp page on PN:
You can get a gastric emptying test done to confirm that. I have to disagree with Karajo on the fiber or Metamucil. My gastroenterologist said absolutely NO fiber, as that's even more difficult for the stomach to process. It was true in my case. My symptoms have improved drastically by avoiding high fiber and cooking and pureeing fruits and veggies. But get tested, and discuss it with a gastroenterologist if you have it. There are a number of things to avoid, like fat, spices, and fiber, so it's a really strange diet, and everyone can tolerate different amounts of each.
Some rheumies are willing to X-ray your joints to look for joint deterioration, and will diagnose RA based on that. It is also possible to have severe joint pain and swelling (but not deterioration) from Sjogren's. I had terrible joint pain, but luckily am getting some relief from Plaquenil. My mom also has Sjogren's and has joint swelling but no joint deterioration.