I've recently been in the same boat as you, having decided it was time to upgrade from Rocky. I suspect there are many grinders in the market at very similar price point and specs - all of which no doubt have a fervent following, and will be recommended in subsequent posts. Being a bit cynical I suspect that you won't see a big difference in the cup unless you're willing to spend up substantially.
My reasons for upgrading, in order of priority, were: Grind retention, consistency, heat transfer, noise. As I only make one coffee per day (21g basket - at 06:30) speed isn't important, but noise is!
The grinders that offer better consistency and less heat transfer than Rocky have larger burrs, and don't solve the issue of retention, in many cases exacerbate it due to being mainly commercial machines, but most of these are faster than Rocky, for the same reason.
Cutting to the chase... I decided to go with the 83mm HG One, currently waiting patiently for delivery, watch this space. I'm pretty sure this grinder is going to polarise the forum, as can be seen from the initial post on the subject, but it ticks all MY boxes - it's the grinder I'd build if I could. It's not cheap though, but nothing a few extra shifts won't sort out.
I have decided not to sell Rocky as I won't get enough of a return, and I want a pour-over grinder for larger groups, so I don't have to change settings of the HG One once dialled in.