Not exactly sure as to what you mean by “with ROBLOX”, but there are plenty of good tutorials on YouTube that can teach you how to use Blender (Can’t really name any from memory, but they’re out there). I believe the tri limit was 10,000 before being changed to 20,000 recently, so keep that in mind. That, and it isn’t possible to export objects as an .FBX file in ROBLOX Studio for some reason.
I’ve been working with Blender since early 2019 and it’s a pretty fun program to work with once you get the hang of it. If you do get into Blender then good luck! 