The 'development roadmap' is a few notes at the end of whatever AAR I am currently writing, plus an occasional trawl through the suggestions thread, plus the very occasional immediate implementation of a suggestion on the day I read it. The level of planning is minimal to none and subject to change without notice, based on my latest whim

The available development time is affected by how much free time I have at the moment, modified by whatever else is distracting me. Last year it was a nine-month trip in a motorhome. Currently, it's RogueTech, which is a great game that I have kept going back to over many years.
Prioritisation is based on whatever I like from the suggestions thread, identified bugs, any generally accepted problems, my current level of enthusiasm and whatever would make the events in my current AAR easier to handle. Occasionally, someone crafts a brilliant proposal backed by evidence, which catches my imagination, and it ends up being a major change to the mechanics.
The UI is usually bodged to accommodate the desired changes with as little modification as possible, although I do sometimes completely revamp certain areas when the level of 'Required Bodgement' gets too high.
Graphics are a low priority and the need for imagination is intended. I use Windows Forms and GDI graphics because that is the fastest and easiest way to implement the mechanics. Aurora is about building an Empire based on the vision you have in your imagination. It is as much an RPG as an exploration and combat game. The more in-game graphics you add, the more you constrain players in that vision of their Empire and their space/ground forces (and the more effort required on non-gameplay elements).
If that sounds like amateur hour, it is! Aurora is one of several different hobbies and its just for fun. It's not in any way a professional, or commercial game. I'm not trying to sell it, or maximise the number of players. I often get suggestions along the lines of: "If you simplified X or made Y automated, or added better graphics, it would attract more people". That is probably true, but the whole point of Aurora is that it is a very niche game for those players who want something that isn't available in commercial games. I created Aurora because I wanted a specific type of game that didn't exist and I ended up sharing the result. There are plenty of options for 4x space games with much better graphics and simpler mechanics
However, if you have specific UI or graphics suggestions that would make the game better without sacrificing the core principles above, or requiring me to spend a lot of time on UI/Graphics - which aren't much fun, please lay out those suggestions and they might be added to the game.