I found I could write much more legibly using a fountain pen, so I've been using them since 1st or 2nd grade. There's a ton of drawbacks to using fountain pens for everything daily. First, while rare, I'd still get leaks and ink on my hands. For instance, if I dropped the pen. Second, there's a bit of a maintenance burden on fountain pens, the nibs need to be cleaned from time to time. Finally, pretty much all of these inks will wash out if the paper gets wet, so it's super bad for legal documents. I like the Pilot Metropolitan fountain pens as they strike the right balance of affordability and quality. The Fine nib for me (correlates to EF from American/European companies) seems to be the sweet spot, Medium feels imprecise for me. Noodler ink seems great, I was previously using Schaeffer ink and it was just ok.
The latest pens I've come enjoy using are Pilot's Frixxion line. I grabbed on a whim awhile back and feel like every student of mathematics should know of these pens. They are a gel pen with fine point options but they can be 'erased' by rubbing a plastic nub on the back against paper. This heats up the paper and causes the ink to disappear. The effect can be reversed by throwing the paper in the freezer if erasure was unintended (or if a notebook was left in an extremely hot cat). I wish I had known about these pens when I was in school. Gel-type pens seem a bit more practical than fountain for daily carry or occasional use, not as good as a fountain but the ink seems to flow better than ballpoint and the tips don't get messed up like a felt pen.
EDIT: More on topic though, I have tried rollerball pens and did not like them. They seemed even less precise than ballpoints for me and skipped more. Terrible writing experience all around, would not do again.