Clicking undo does not undo tapping a token artifact meteorite created by Roxanne
#Undo button on Meteorite Artifact Tokens
spark vigil
tame oak
The interaction between the Meteorite token's mana ability and the second triggered ability on Roxanne that adds another mana of the same type the token produced is the issue here. A Forest enchanted with [[Wild Growth]] behaves the same way.
On desktop-1.6.65-SNAPSHOT-09-04 without Roxanne on the field, the Meteorite token untaps if you click "Undo". Note that there may be a visual glitch where the token appears tapped but either clicking it will activate the mana ability again or moving forward in the turn will have it visually untap.
As to why the combination of an activated and triggered mana ability can't be rolled back, not my expertise I'm afraid.
slim plankBOT
Enchantment — Aura
Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional 
.
If you stop to listen, you can hear it grow.
frank nova
Ya, the basic undo system doesn't know how to "unpay" these types of effects, so they get marked as "not undoable" the mana should still be in your mana pool in your player panel. We do have an experimental undo restore feature that would roll back the whole turn. We still have a few kinks to work out with that, but if you find yourself needing to undo a lot, it might be more consistent. (It is still experimental!)
spark vigil
How do you try using the undo turn option?