And where would they buy the roubles? And with what? However you cut it, buying gas from Russia means sending them EUR somehow. So the rouble thing is just a divertion from the real issue, which is people dying in Ukraine.
[1] https://www.youtube.com/c/%D0%9C%D0%B0%D1%80%D0%B8%D1%83%D0%...
[2] https://www.youtube.com/channel/UCqcmvyHrmrmIC7nM1sA3_Uw/vid...