Yes you can run SlimeRancher with that good setup
I'm running it on a potato at the moment (Have the option to run it on a mac as well :P)
No a public roadmap does not exist at the moment. I would consider this as a closed alpha phase of the game and isn't as open as other open beta games (War Thunder, Unturned, etc.)
I can tell you, YES there is a roadmap, I've seen screenshots of it before however as I've asked before: