I'd say that your wheel rolling the fill to compact red clay will essentially guarantee slab failure. If you want to try to see if it will work, you can have a materials testing company come out, take a sample, run a lab density test, and test the in-place density to verify how well your compaction compares to the lab density. If by some incredible luck, you had the clay at the right moisture level, and rolled it enough, in thin enough lifts to work, the testing will verify that. If it doesn't test to minimum requirements, there is no remediating it by more compaction; it will have to be removed and replaced with proper compaction done during the replacement.
Clay is one of the hardest materials to compact, and also the material that generally settles the worst. It will appear to be real hard, but often that is just the top few inches, it bridges and compactive effort doesn't go much below the surface. As the moisture level changes in it over time, it shrinks and settles terribly, with resulting slab failure.
Early in my career, I was hired to do a forensic analysis and act as an expert witness against a home builder that had filled about 30 inches at the back of a garage floor that was on a slope. The concrete had settled and cracked severely. He had wheel rolled and then used a plate compactor to pack the clay backfill, and then put some gravel and sand on top before doing the slab. When we demo'd out the concrete and measured, we found that the clay had settled about 6 inches (out of 30" total fill depth) at the back of the garage. That was nearly 25% of the initial clay thickness. That was an extreme case, but 10% shrinkage is fairly common, and enough to cause extreme concrete slab failure.
Personally, I'd remove all the fill you have had placed so far, down to original earth, and then replace it with either crushed rock, or re-use the clay, after mixing it to correct water content (based on a test and recommendation from a testing lab) and compacting it with proper equipment for the clay, and testing the results to verify you have got to proper compaction as you go along. Truthfully, it is usually cheaper to just buy 3/4" minus road base gravel to do your backfill than it is to test the clay, and mess around with what needs done to compact it.
You can compact 3/4" minus gravel by visual inspection if you are familiar with doing that, although to be safe you should also have it tested as you compact it. Visually monitoring clay compaction is usually meaningless, even if you have a lot of experience working with that exact material. It is just too hard to judge without testing. I have several million cubic yards of experience in working in large excavation projects on clay soil to back up that opinion. All of that experience was with lab controlled samples and on-site testing, and several years of that was with me running the nuclear guage doing the field testing and adjusting the field procedures to meet the compaction specs.
