It’s good but thank you! I found the solution:
Ensure RootPart / HumanoidRootPart is anchored prior to exporting.
Ensure Model is exported at origin (0, 0, 0)
In Blender, keep origins set to World origin.
When rigging use ‘Node Only’ feature.
Using all of these I was able to export and re-import perfectly. 
I tried doing the exact steps shown in the post but whenever I import an animation the rig just doesn’t move at all, does anyone know how to fix this?
Nice to hear that you figured it out.
Its probably also import for everyone to know this knowledge as I know a lot of problems can occur when exporting/importing.
Are you playing it in the Animation Editor or when playing the game?
Because the anination won’t play in game unleds the animation is called in a script.
Late reply but this is how legacy is supposed to work. Roblox messes up part names when exporting humanoids for whatever reason (very annoying) so you have to manually rename the parts to match the bone and click “constraint matching parts”. The regular export deletes the humanoid and leaves part names in tact but mesh and texturing suffer.
Does anyone know how to fix this? I’m still pretty new to the plugin
In blender I made a test animation which works fine, but when I export it to studio the orientation and the position of the handle change
Studio:
May I ask where exactly it exports the rig? Because I still cannot find the path or anything relevant to where it exports the rig, I searched everything but couldn’t find the export data.
Does this plugin include fixing the bones’ random orientations when importing? I have my ROBLOX rig with perfectly placed joints, but whenever I rebuild the rig after importing in blender, it just has ruined bones with random angles, and it really ruins my setup. Or is there already a solution?
This is the example of my rig’s hand with the bones like this:
I have an issue where only the head bone is displayed when I press rebuild rig.
I checked a reddit post that came across this issue and tried the solution but it didn’t work for me.
So far the versions I’ve tried are 2.8, 4.0, and 3.5.
Any ideas?
Alright nevermind this plugin is not good for use, better plugin: Blender rig exporter/animation importer - #1628 by CAUTlONED
If you had the same issue as me, this’ll work.
If anyone is having trouble with bones not showing after rebuilding rig:
Make sure to enable “Show overlays” at the top right 
Is there a way to export an animation made in roblox to use it in blender?
is there a way to edit a keyframes position/rotation like in the roblox animation editor?
Select a bone and go to the section “item” of the n-panel
You might also want to change the rotation mode:
IIRC the default is quaternion.
What is showing on your viewport isn’t always what’s registering on the animation, take a look at your keyframes and see if everything is keyed and correct:
also, make sure auto-keying is on.
It could be something else but since you only provided a screenshot of your viewport I can only think that something is wrong in your timeline/keyframes.
What version of Blender, the addon, and the Roblox plugin are you using? Also, are you using Den_S’s version or Cautioned’s?
To be honest, I have no idea what could be causing this, but I’m using Blender 4.0, the Blender addon version 1.9.6, and the latest version of the Roblox plugin and I’ve had no issues (I use r15 though). Both Blender addon and Roblox plugin from cautioned’s fork.
blender 4.1 and den_s’s version
it seems the rotation x is inverted (75 in roblox = -75 in blender)
and that y rotation in roblox animation editor is z rotation in blender xyz euler
the location is still off though
