Has anyone painted their car with rollers

You're saying you didn't thin it at all? How many coats did you apply?
It has been several years. I recall adding a little thinner (what Interlux suggests), but only when needed. I recall starting out full strength on both jobs and adding a little thinner to the tray if the foam brush starts chattering. That happens more on a hot day and if you leave the paint in the tray long, so depends on how fast you are. In sum, you add thinner only as needed to keep the paint at the original consistency. I will probably have to re-learn it for my Dart interior and exterior, but will do the floor first where mistakes aren't seen anyway.

I recall doing 2 coats for both the trailer and Dart trunk & engine bay. The trailer had existing white paint. The Dart was bare metal, mostly shiny with just a few pits in the corners under the cowl I couldn't sand out in the bay and some rust left in the trunk wheel well. I primed w/ Rust Destroyer (red), then Interlux white primer, then 2 coats light yellow Brightsides. Between coats of Brightsides you must sand w/ 600 grit to remove the gloss. I didn't sand the final coat since it was very shiny. I has Teflon that floats to the surface and helps keep dirt off. If you final sand, it might remove that Teflon layer.